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	$90.90	11.588%	$101.4335	$101.43	$101.45	$101.40
Purchase #2	$243.55	10.829%	$269.924	$269.92	$269.90	$269.90
Purchase #3	$93.65	12.314%	$105.1821	$105.18	$105.20	$105.20
Purchase #4	$138.63	3.807%	$143.9076	$143.91	$143.90	$143.90
Purchase #5	$45.74	10.551%	$50.566	$50.57	$50.55	$50.60
Purchase #6	$10.93	11.210%	$12.1553	$12.16	$12.15	$12.20
Purchase #7	$31.30	7.151%	$33.5383	$33.54	$33.55	$33.50
7 purchase totals =	$654.70		$716.7068	$716.71	$716.70	$716.70