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	$40.42	12.234%	$45.365	$45.37	$45.35	$45.40
Purchase #2	$99.72	7.113%	$106.8131	$106.81	$106.80	$106.80
Purchase #3	$71.33	8.830%	$77.6284	$77.63	$77.65	$77.60
Purchase #4	$112.83	13.389%	$127.9368	$127.94	$127.95	$127.90
Purchase #5	$38.64	12.237%	$43.3684	$43.37	$43.35	$43.40
Purchase #6	$186.63	13.725%	$212.245	$212.25	$212.25	$212.20
Purchase #7	$163.71	9.384%	$179.0725	$179.07	$179.05	$179.10
7 purchase totals =	$713.28		$792.4292	$792.44	$792.40	$792.40