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	$166.90	13.753%	$189.8538	$189.85	$189.85	$189.90
Purchase #2	$57.55	9.348%	$62.9298	$62.93	$62.95	$62.90
Purchase #3	$190.92	11.166%	$212.2381	$212.24	$212.25	$212.20
Purchase #4	$33.68	13.853%	$38.3457	$38.35	$38.35	$38.30
Purchase #5	$132.69	6.324%	$141.0813	$141.08	$141.10	$141.10
Purchase #6	$145.56	12.701%	$164.0476	$164.05	$164.05	$164.00
Purchase #7	$91.52	8.414%	$99.2205	$99.22	$99.20	$99.20
7 purchase totals =	$818.82		$907.7168	$907.72	$907.75	$907.60