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	$236.43	13.589%	$268.5585	$268.56	$268.55	$268.60
Purchase #2	$94.25	6.405%	$100.2867	$100.29	$100.30	$100.30
Purchase #3	$105.56	12.503%	$118.7582	$118.76	$118.75	$118.80
Purchase #4	$198.50	7.217%	$212.8257	$212.83	$212.85	$212.80
Purchase #5	$151.64	13.695%	$172.4071	$172.41	$172.40	$172.40
Purchase #6	$236.38	10.647%	$261.5474	$261.55	$261.55	$261.50
Purchase #7	$213.53	4.120%	$222.3274	$222.33	$222.35	$222.30
7 purchase totals =	$1,236.29		$1,356.7110	$1,356.73	$1,356.75	$1,356.70