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	$230.68	12.329%	$259.1205	$259.12	$259.10	$259.10
Purchase #2	$85.58	4.666%	$89.5732	$89.57	$89.55	$89.60
Purchase #3	$186.66	5.171%	$196.3122	$196.31	$196.30	$196.30
Purchase #4	$246.62	13.861%	$280.804	$280.80	$280.80	$280.80
Purchase #5	$146.41	4.588%	$153.1273	$153.13	$153.15	$153.10
Purchase #6	$83.90	12.255%	$94.1819	$94.18	$94.20	$94.20
Purchase #7	$77.33	7.817%	$83.3749	$83.37	$83.35	$83.40
7 purchase totals =	$1,057.18		$1,156.4940	$1,156.48	$1,156.45	$1,156.50