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	$250.44	9.859%	$275.1309	$275.13	$275.15	$275.10
Purchase #2	$11.85	13.198%	$13.414	$13.41	$13.40	$13.40
Purchase #3	$6.36	13.136%	$7.1954	$7.20	$7.20	$7.20
Purchase #4	$245.28	4.430%	$256.1459	$256.15	$256.15	$256.10
Purchase #5	$43.76	4.675%	$45.8058	$45.81	$45.80	$45.80
Purchase #6	$64.67	11.549%	$72.1387	$72.14	$72.15	$72.10
Purchase #7	$24.95	5.500%	$26.3223	$26.32	$26.30	$26.30
7 purchase totals =	$647.31		$696.1530	$696.16	$696.15	$696.00