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	$239.75	3.783%	$248.8197	$248.82	$248.80	$248.80
Purchase #2	$11.61	7.228%	$12.4492	$12.45	$12.45	$12.40
Purchase #3	$211.63	5.628%	$223.5405	$223.54	$223.55	$223.50
Purchase #4	$249.87	4.530%	$261.1891	$261.19	$261.20	$261.20
Purchase #5	$144.28	7.637%	$155.2987	$155.30	$155.30	$155.30
Purchase #6	$36.78	9.752%	$40.3668	$40.37	$40.35	$40.40
Purchase #7	$87.44	3.590%	$90.5791	$90.58	$90.60	$90.60
7 purchase totals =	$981.36		$1,032.2431	$1,032.25	$1,032.25	$1,032.20