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	$143.89	5.298%	$151.5133	$151.51	$151.50	$151.50
Purchase #2	$45.87	6.573%	$48.885	$48.89	$48.90	$48.90
Purchase #3	$213.54	7.337%	$229.2074	$229.21	$229.20	$229.20
Purchase #4	$47.68	9.306%	$52.1171	$52.12	$52.10	$52.10
Purchase #5	$141.43	5.788%	$149.616	$149.62	$149.60	$149.60
Purchase #6	$102.89	12.769%	$116.028	$116.03	$116.05	$116.00
Purchase #7	$191.55	12.380%	$215.2639	$215.26	$215.25	$215.30
7 purchase totals =	$886.85		$962.6307	$962.64	$962.60	$962.60