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	$72.54	6.655%	$77.3675	$77.37	$77.35	$77.40
Purchase #2	$148.77	3.481%	$153.9487	$153.95	$153.95	$153.90
Purchase #3	$19.50	3.262%	$20.1361	$20.14	$20.15	$20.10
Purchase #4	$244.59	13.393%	$277.3479	$277.35	$277.35	$277.30
Purchase #5	$191.56	13.775%	$217.9474	$217.95	$217.95	$217.90
Purchase #6	$87.77	5.873%	$92.9247	$92.92	$92.90	$92.90
Purchase #7	$63.83	13.792%	$72.6334	$72.63	$72.65	$72.60
7 purchase totals =	$828.56		$912.3057	$912.31	$912.30	$912.10