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	$146.52	3.651%	$151.8694	$151.87	$151.85	$151.90
Purchase #2	$6.35	11.760%	$7.0968	$7.10	$7.10	$7.10
Purchase #3	$91.35	9.605%	$100.1242	$100.12	$100.10	$100.10
Purchase #4	$12.28	13.437%	$13.9301	$13.93	$13.95	$13.90
Purchase #5	$231.88	10.614%	$256.4917	$256.49	$256.50	$256.50
Purchase #6	$141.75	4.216%	$147.7262	$147.73	$147.75	$147.70
Purchase #7	$88.82	12.530%	$99.9491	$99.95	$99.95	$99.90
7 purchase totals =	$718.95		$777.1875	$777.19	$777.20	$777.10