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	$95.45	5.431%	$100.6339	$100.63	$100.65	$100.60
Purchase #2	$94.33	5.519%	$99.5361	$99.54	$99.55	$99.50
Purchase #3	$216.81	11.465%	$241.6673	$241.67	$241.65	$241.70
Purchase #4	$66.34	7.859%	$71.5537	$71.55	$71.55	$71.60
Purchase #5	$204.41	10.379%	$225.6257	$225.63	$225.65	$225.60
Purchase #6	$55.84	11.450%	$62.2337	$62.23	$62.25	$62.20
Purchase #7	$249.47	7.371%	$267.8584	$267.86	$267.85	$267.90
7 purchase totals =	$982.65		$1,069.1088	$1,069.11	$1,069.15	$1,069.10