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	$186.98	11.303%	$208.1143	$208.11	$208.10	$208.10
Purchase #2	$214.28	3.862%	$222.5555	$222.56	$222.55	$222.60
Purchase #3	$122.35	4.367%	$127.693	$127.69	$127.70	$127.70
Purchase #4	$154.52	10.298%	$170.4325	$170.43	$170.45	$170.40
Purchase #5	$164.35	9.675%	$180.2509	$180.25	$180.25	$180.30
Purchase #6	$29.28	12.401%	$32.911	$32.91	$32.90	$32.90
Purchase #7	$82.96	12.357%	$93.2114	$93.21	$93.20	$93.20
7 purchase totals =	$954.72		$1,035.1686	$1,035.16	$1,035.15	$1,035.20