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	$151.57	3.743%	$157.2433	$157.24	$157.25	$157.20
Purchase #2	$116.59	5.763%	$123.3091	$123.31	$123.30	$123.30
Purchase #3	$219.27	13.164%	$248.1347	$248.13	$248.15	$248.10
Purchase #4	$52.73	13.729%	$59.9693	$59.97	$59.95	$60.00
Purchase #5	$105.49	11.201%	$117.3059	$117.31	$117.30	$117.30
Purchase #6	$214.53	11.357%	$238.8942	$238.89	$238.90	$238.90
Purchase #7	$142.47	12.185%	$159.83	$159.83	$159.85	$159.80
7 purchase totals =	$1,002.65		$1,104.6865	$1,104.68	$1,104.70	$1,104.60