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	$185.94	5.681%	$196.5033	$196.50	$196.50	$196.50
Purchase #2	$54.56	9.487%	$59.7361	$59.74	$59.75	$59.70
Purchase #3	$226.40	9.202%	$247.2333	$247.23	$247.25	$247.20
Purchase #4	$114.89	12.339%	$129.0663	$129.07	$129.05	$129.10
Purchase #5	$223.44	11.489%	$249.111	$249.11	$249.10	$249.10
Purchase #6	$34.89	7.647%	$37.558	$37.56	$37.55	$37.60
Purchase #7	$208.83	10.837%	$231.4609	$231.46	$231.45	$231.50
7 purchase totals =	$1,048.95		$1,150.6689	$1,150.67	$1,150.65	$1,150.70