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	$67.27	6.329%	$71.5275	$71.53	$71.55	$71.50
Purchase #2	$69.43	3.445%	$71.8219	$71.82	$71.80	$71.80
Purchase #3	$50.46	3.626%	$52.2897	$52.29	$52.30	$52.30
Purchase #4	$117.58	8.680%	$127.7859	$127.79	$127.80	$127.80
Purchase #5	$114.75	12.565%	$129.1683	$129.17	$129.15	$129.20
Purchase #6	$174.77	12.439%	$196.5096	$196.51	$196.50	$196.50
Purchase #7	$44.34	3.764%	$46.009	$46.01	$46.00	$46.00
7 purchase totals =	$638.60		$695.1119	$695.12	$695.10	$695.10