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	$85.89	12.516%	$96.64	$96.64	$96.65	$96.60
Purchase #2	$99.31	4.445%	$103.7243	$103.72	$103.70	$103.70
Purchase #3	$54.26	7.707%	$58.4418	$58.44	$58.45	$58.40
Purchase #4	$43.75	8.769%	$47.5864	$47.59	$47.60	$47.60
Purchase #5	$40.59	6.726%	$43.3201	$43.32	$43.30	$43.30
Purchase #6	$180.70	10.720%	$200.071	$200.07	$200.05	$200.10
Purchase #7	$110.43	13.680%	$125.5368	$125.54	$125.55	$125.50
7 purchase totals =	$614.93		$675.3204	$675.32	$675.30	$675.20