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	$44.79	13.714%	$50.9325	$50.93	$50.95	$50.90
Purchase #2	$41.36	3.499%	$42.8072	$42.81	$42.80	$42.80
Purchase #3	$139.56	4.545%	$145.903	$145.90	$145.90	$145.90
Purchase #4	$101.52	6.800%	$108.4234	$108.42	$108.40	$108.40
Purchase #5	$42.69	6.163%	$45.321	$45.32	$45.30	$45.30
Purchase #6	$83.34	7.450%	$89.5488	$89.55	$89.55	$89.50
Purchase #7	$212.39	8.669%	$230.8021	$230.80	$230.80	$230.80
7 purchase totals =	$665.65		$713.7380	$713.73	$713.70	$713.60