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	$130.65	5.403%	$137.709	$137.71	$137.70	$137.70
Purchase #2	$167.37	4.659%	$175.1678	$175.17	$175.15	$175.20
Purchase #3	$182.76	7.536%	$196.5328	$196.53	$196.55	$196.50
Purchase #4	$151.91	5.702%	$160.5719	$160.57	$160.55	$160.60
Purchase #5	$57.60	9.802%	$63.246	$63.25	$63.25	$63.20
Purchase #6	$184.89	3.428%	$191.228	$191.23	$191.25	$191.20
Purchase #7	$6.43	10.242%	$7.0886	$7.09	$7.10	$7.10
7 purchase totals =	$881.61		$931.5441	$931.55	$931.55	$931.50