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	$81.36	11.230%	$90.4967	$90.50	$90.50	$90.50
Purchase #2	$23.38	3.170%	$24.1211	$24.12	$24.10	$24.10
Purchase #3	$237.62	11.733%	$265.5	$265.50	$265.50	$265.50
Purchase #4	$51.64	5.460%	$54.4595	$54.46	$54.45	$54.50
Purchase #5	$85.57	11.358%	$95.289	$95.29	$95.30	$95.30
Purchase #6	$113.76	10.262%	$125.4341	$125.43	$125.45	$125.40
Purchase #7	$85.50	12.781%	$96.4278	$96.43	$96.45	$96.40
7 purchase totals =	$678.83		$751.7282	$751.73	$751.75	$751.70