Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.83	10.595%	$152.4331	$152.43	$152.45	$152.40
Purchase #2	$244.61	8.658%	$265.7883	$265.79	$265.80	$265.80
Purchase #3	$136.78	12.383%	$153.7175	$153.72	$153.70	$153.70
Purchase #4	$234.83	5.707%	$248.2317	$248.23	$248.25	$248.20
Purchase #5	$187.43	10.646%	$207.3838	$207.38	$207.40	$207.40
Purchase #6	$234.25	12.635%	$263.8475	$263.85	$263.85	$263.80
Purchase #7	$136.81	11.463%	$152.4925	$152.49	$152.50	$152.50
7 purchase totals =	$1,312.54		$1,443.8944	$1,443.89	$1,443.95	$1,443.80