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	$115.27	11.171%	$128.1468	$128.15	$128.15	$128.10
Purchase #2	$127.55	13.785%	$145.1328	$145.13	$145.15	$145.10
Purchase #3	$81.88	5.635%	$86.4939	$86.49	$86.50	$86.50
Purchase #4	$212.35	4.607%	$222.133	$222.13	$222.15	$222.10
Purchase #5	$113.29	12.381%	$127.3164	$127.32	$127.30	$127.30
Purchase #6	$77.39	10.453%	$85.4796	$85.48	$85.50	$85.50
Purchase #7	$24.62	7.607%	$26.4928	$26.49	$26.50	$26.50
7 purchase totals =	$752.35		$821.1953	$821.19	$821.25	$821.10