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	$40.85	12.683%	$46.031	$46.03	$46.05	$46.00
Purchase #2	$232.42	4.786%	$243.5436	$243.54	$243.55	$243.50
Purchase #3	$208.41	7.391%	$223.8136	$223.81	$223.80	$223.80
Purchase #4	$49.79	10.688%	$55.1116	$55.11	$55.10	$55.10
Purchase #5	$82.95	3.523%	$85.8723	$85.87	$85.85	$85.90
Purchase #6	$89.77	10.678%	$99.3556	$99.36	$99.35	$99.40
Purchase #7	$125.49	4.761%	$131.4646	$131.46	$131.45	$131.50
7 purchase totals =	$829.68		$885.1923	$885.18	$885.15	$885.20