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	$188.60	4.514%	$197.1134	$197.11	$197.10	$197.10
Purchase #2	$122.48	7.697%	$131.9073	$131.91	$131.90	$131.90
Purchase #3	$93.80	6.232%	$99.6456	$99.65	$99.65	$99.60
Purchase #4	$110.62	11.542%	$123.3878	$123.39	$123.40	$123.40
Purchase #5	$123.58	3.681%	$128.129	$128.13	$128.15	$128.10
Purchase #6	$243.35	12.527%	$273.8345	$273.83	$273.85	$273.80
Purchase #7	$125.44	6.460%	$133.5434	$133.54	$133.55	$133.50
7 purchase totals =	$1,007.87		$1,087.5610	$1,087.56	$1,087.60	$1,087.40