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	$37.30	11.362%	$41.538	$41.54	$41.55	$41.50
Purchase #2	$233.29	7.805%	$251.4983	$251.50	$251.50	$251.50
Purchase #3	$222.97	10.188%	$245.6862	$245.69	$245.70	$245.70
Purchase #4	$192.74	10.758%	$213.475	$213.48	$213.50	$213.50
Purchase #5	$53.39	11.334%	$59.4412	$59.44	$59.45	$59.40
Purchase #6	$153.95	13.299%	$174.4238	$174.42	$174.40	$174.40
Purchase #7	$54.61	3.387%	$56.4596	$56.46	$56.45	$56.50
7 purchase totals =	$948.25		$1,042.5221	$1,042.53	$1,042.55	$1,042.50