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	$143.56	6.243%	$152.5225	$152.52	$152.50	$152.50
Purchase #2	$54.95	12.405%	$61.7665	$61.77	$61.75	$61.80
Purchase #3	$230.78	12.396%	$259.3875	$259.39	$259.40	$259.40
Purchase #4	$162.29	11.176%	$180.4275	$180.43	$180.45	$180.40
Purchase #5	$22.42	12.459%	$25.2133	$25.21	$25.20	$25.20
Purchase #6	$182.87	8.531%	$198.4706	$198.47	$198.45	$198.50
Purchase #7	$244.33	9.465%	$267.4558	$267.46	$267.45	$267.50
7 purchase totals =	$1,041.20		$1,145.2437	$1,145.25	$1,145.20	$1,145.30