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	$191.61	3.389%	$198.1037	$198.10	$198.10	$198.10
Purchase #2	$42.60	7.331%	$45.723	$45.72	$45.70	$45.70
Purchase #3	$68.91	4.410%	$71.9489	$71.95	$71.95	$71.90
Purchase #4	$9.31	10.853%	$10.3204	$10.32	$10.30	$10.30
Purchase #5	$125.87	5.520%	$132.818	$132.82	$132.80	$132.80
Purchase #6	$109.59	13.816%	$124.731	$124.73	$124.75	$124.70
Purchase #7	$137.79	10.242%	$151.9025	$151.90	$151.90	$151.90
7 purchase totals =	$685.68		$735.5475	$735.54	$735.50	$735.40