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	$145.51	5.272%	$153.1813	$153.18	$153.20	$153.20
Purchase #2	$134.77	11.569%	$150.3615	$150.36	$150.35	$150.40
Purchase #3	$233.32	13.495%	$264.8065	$264.81	$264.80	$264.80
Purchase #4	$242.40	4.740%	$253.8898	$253.89	$253.90	$253.90
Purchase #5	$113.43	6.496%	$120.7984	$120.80	$120.80	$120.80
Purchase #6	$41.73	10.636%	$46.1684	$46.17	$46.15	$46.20
Purchase #7	$37.57	8.563%	$40.7871	$40.79	$40.80	$40.80
7 purchase totals =	$948.73		$1,029.9930	$1,030.00	$1,030.00	$1,030.10