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	$188.93	10.179%	$208.1612	$208.16	$208.15	$208.20
Purchase #2	$202.73	5.274%	$213.422	$213.42	$213.40	$213.40
Purchase #3	$33.56	3.561%	$34.7551	$34.76	$34.75	$34.80
Purchase #4	$212.71	5.856%	$225.1663	$225.17	$225.15	$225.20
Purchase #5	$33.86	12.850%	$38.211	$38.21	$38.20	$38.20
Purchase #6	$90.97	9.174%	$99.3156	$99.32	$99.30	$99.30
Purchase #7	$167.25	12.693%	$188.479	$188.48	$188.50	$188.50
7 purchase totals =	$930.01		$1,007.5102	$1,007.52	$1,007.45	$1,007.60