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	$50.50	12.772%	$56.9499	$56.95	$56.95	$56.90
Purchase #2	$181.98	11.766%	$203.3918	$203.39	$203.40	$203.40
Purchase #3	$171.45	11.674%	$191.4651	$191.47	$191.45	$191.50
Purchase #4	$220.56	11.271%	$245.4193	$245.42	$245.40	$245.40
Purchase #5	$134.93	6.392%	$143.5547	$143.55	$143.55	$143.60
Purchase #6	$13.93	5.463%	$14.691	$14.69	$14.70	$14.70
Purchase #7	$229.87	6.534%	$244.8897	$244.89	$244.90	$244.90
7 purchase totals =	$1,003.22		$1,100.3615	$1,100.36	$1,100.35	$1,100.40