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	$35.58	4.219%	$37.0811	$37.08	$37.10	$37.10
Purchase #2	$56.43	5.871%	$59.743	$59.74	$59.75	$59.70
Purchase #3	$50.85	4.730%	$53.2552	$53.26	$53.25	$53.30
Purchase #4	$64.39	13.430%	$73.0376	$73.04	$73.05	$73.00
Purchase #5	$105.84	3.831%	$109.8947	$109.89	$109.90	$109.90
Purchase #6	$120.66	3.223%	$124.5489	$124.55	$124.55	$124.50
Purchase #7	$78.37	8.286%	$84.8637	$84.86	$84.85	$84.90
7 purchase totals =	$512.12		$542.4242	$542.42	$542.45	$542.40