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	$235.87	6.559%	$251.3407	$251.34	$251.35	$251.30
Purchase #2	$154.49	3.459%	$159.8338	$159.83	$159.85	$159.80
Purchase #3	$11.32	6.807%	$12.0906	$12.09	$12.10	$12.10
Purchase #4	$148.82	11.685%	$166.2096	$166.21	$166.20	$166.20
Purchase #5	$67.69	7.337%	$72.6564	$72.66	$72.65	$72.70
Purchase #6	$122.78	4.683%	$128.5298	$128.53	$128.55	$128.50
Purchase #7	$225.76	7.851%	$243.4844	$243.48	$243.50	$243.50
7 purchase totals =	$966.73		$1,034.1453	$1,034.14	$1,034.20	$1,034.10