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	$37.46	3.479%	$38.7632	$38.76	$38.75	$38.80
Purchase #2	$120.45	13.850%	$137.1323	$137.13	$137.15	$137.10
Purchase #3	$47.42	4.460%	$49.5349	$49.53	$49.55	$49.50
Purchase #4	$14.84	11.425%	$16.5355	$16.54	$16.55	$16.50
Purchase #5	$32.59	7.676%	$35.0916	$35.09	$35.10	$35.10
Purchase #6	$128.94	3.248%	$133.128	$133.13	$133.15	$133.10
Purchase #7	$248.92	3.362%	$257.2887	$257.29	$257.30	$257.30
7 purchase totals =	$630.62		$667.4742	$667.47	$667.55	$667.40