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	$169.55	3.731%	$175.8759	$175.88	$175.90	$175.90
Purchase #2	$88.67	13.324%	$100.4844	$100.48	$100.50	$100.50
Purchase #3	$200.49	12.450%	$225.451	$225.45	$225.45	$225.50
Purchase #4	$58.72	4.748%	$61.508	$61.51	$61.50	$61.50
Purchase #5	$57.33	4.329%	$59.8118	$59.81	$59.80	$59.80
Purchase #6	$90.80	10.605%	$100.4293	$100.43	$100.45	$100.40
Purchase #7	$123.53	3.489%	$127.84	$127.84	$127.85	$127.80
7 purchase totals =	$789.09		$851.4004	$851.40	$851.45	$851.40