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	$223.25	5.231%	$234.9282	$234.93	$234.95	$234.90
Purchase #2	$165.83	12.105%	$185.9037	$185.90	$185.90	$185.90
Purchase #3	$211.89	4.475%	$221.3721	$221.37	$221.35	$221.40
Purchase #4	$92.51	4.360%	$96.5434	$96.54	$96.55	$96.50
Purchase #5	$12.63	5.350%	$13.3057	$13.31	$13.30	$13.30
Purchase #6	$184.42	7.521%	$198.2902	$198.29	$198.30	$198.30
Purchase #7	$32.27	9.328%	$35.2801	$35.28	$35.30	$35.30
7 purchase totals =	$922.80		$985.6234	$985.62	$985.65	$985.60