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	$105.59	5.411%	$111.3035	$111.30	$111.30	$111.30
Purchase #2	$76.49	8.364%	$82.8876	$82.89	$82.90	$82.90
Purchase #3	$151.65	10.455%	$167.505	$167.51	$167.50	$167.50
Purchase #4	$119.91	12.272%	$134.6254	$134.63	$134.65	$134.60
Purchase #5	$59.68	11.221%	$66.3767	$66.38	$66.40	$66.40
Purchase #6	$162.34	6.671%	$173.1697	$173.17	$173.15	$173.20
Purchase #7	$226.87	8.126%	$245.3055	$245.31	$245.30	$245.30
7 purchase totals =	$902.53		$981.1734	$981.19	$981.20	$981.20