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	$178.99	6.172%	$190.0373	$190.04	$190.05	$190.00
Purchase #2	$23.56	11.792%	$26.3382	$26.34	$26.35	$26.30
Purchase #3	$219.90	13.813%	$250.2748	$250.27	$250.25	$250.30
Purchase #4	$116.79	9.187%	$127.5195	$127.52	$127.50	$127.50
Purchase #5	$199.81	11.444%	$222.6763	$222.68	$222.70	$222.70
Purchase #6	$124.35	13.232%	$140.804	$140.80	$140.80	$140.80
Purchase #7	$149.61	4.787%	$156.7718	$156.77	$156.75	$156.80
7 purchase totals =	$1,013.01		$1,114.4219	$1,114.42	$1,114.40	$1,114.40