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	$39.71	13.821%	$45.1983	$45.20	$45.20	$45.20
Purchase #2	$77.69	10.313%	$85.7022	$85.70	$85.70	$85.70
Purchase #3	$49.77	11.148%	$55.3184	$55.32	$55.30	$55.30
Purchase #4	$214.72	3.642%	$222.5401	$222.54	$222.55	$222.50
Purchase #5	$182.35	6.604%	$194.3924	$194.39	$194.40	$194.40
Purchase #6	$236.34	11.185%	$262.7746	$262.77	$262.75	$262.80
Purchase #7	$185.34	5.399%	$195.3465	$195.35	$195.35	$195.30
7 purchase totals =	$985.92		$1,061.2725	$1,061.27	$1,061.25	$1,061.20