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	$219.50	6.411%	$233.5721	$233.57	$233.55	$233.60
Purchase #2	$59.91	10.269%	$66.0622	$66.06	$66.05	$66.10
Purchase #3	$237.85	11.810%	$265.9401	$265.94	$265.95	$265.90
Purchase #4	$126.79	3.867%	$131.693	$131.69	$131.70	$131.70
Purchase #5	$188.70	10.768%	$209.0192	$209.02	$209.00	$209.00
Purchase #6	$81.26	6.588%	$86.6134	$86.61	$86.60	$86.60
Purchase #7	$136.89	12.431%	$153.9068	$153.91	$153.90	$153.90
7 purchase totals =	$1,050.90		$1,146.8068	$1,146.80	$1,146.75	$1,146.80