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	$61.78	8.810%	$67.2228	$67.22	$67.20	$67.20
Purchase #2	$132.99	3.264%	$137.3308	$137.33	$137.35	$137.30
Purchase #3	$126.62	3.859%	$131.5063	$131.51	$131.50	$131.50
Purchase #4	$105.76	11.343%	$117.7564	$117.76	$117.75	$117.80
Purchase #5	$114.42	9.391%	$125.1652	$125.17	$125.15	$125.20
Purchase #6	$99.40	4.173%	$103.548	$103.55	$103.55	$103.50
Purchase #7	$36.76	7.697%	$39.5894	$39.59	$39.60	$39.60
7 purchase totals =	$677.73		$722.1189	$722.13	$722.10	$722.10