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	$135.99	13.168%	$153.8972	$153.90	$153.90	$153.90
Purchase #2	$41.59	9.511%	$45.5456	$45.55	$45.55	$45.50
Purchase #3	$107.41	3.219%	$110.8675	$110.87	$110.85	$110.90
Purchase #4	$76.27	7.597%	$82.0642	$82.06	$82.05	$82.10
Purchase #5	$134.47	6.138%	$142.7238	$142.72	$142.70	$142.70
Purchase #6	$155.61	12.549%	$175.1375	$175.14	$175.15	$175.10
Purchase #7	$170.97	10.180%	$188.3747	$188.37	$188.35	$188.40
7 purchase totals =	$822.31		$898.6105	$898.61	$898.55	$898.60