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	$61.79	12.428%	$69.4693	$69.47	$69.45	$69.50
Purchase #2	$234.33	13.798%	$266.6629	$266.66	$266.65	$266.70
Purchase #3	$166.53	8.504%	$180.6917	$180.69	$180.70	$180.70
Purchase #4	$33.53	11.348%	$37.335	$37.34	$37.35	$37.30
Purchase #5	$244.72	7.713%	$263.5953	$263.60	$263.60	$263.60
Purchase #6	$243.84	5.112%	$256.3051	$256.31	$256.30	$256.30
Purchase #7	$54.72	4.294%	$57.0697	$57.07	$57.05	$57.10
7 purchase totals =	$1,039.46		$1,131.1290	$1,131.14	$1,131.10	$1,131.20