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	$43.76	4.595%	$45.7708	$45.77	$45.75	$45.80
Purchase #2	$69.58	13.169%	$78.743	$78.74	$78.75	$78.70
Purchase #3	$89.71	6.867%	$95.8704	$95.87	$95.85	$95.90
Purchase #4	$8.91	11.622%	$9.9455	$9.95	$9.95	$9.90
Purchase #5	$114.49	7.562%	$123.1477	$123.15	$123.15	$123.10
Purchase #6	$79.70	11.550%	$88.9054	$88.91	$88.90	$88.90
Purchase #7	$179.61	10.860%	$199.1156	$199.12	$199.10	$199.10
7 purchase totals =	$585.76		$641.4984	$641.51	$641.45	$641.40