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	$59.41	5.859%	$62.8908	$62.89	$62.90	$62.90
Purchase #2	$130.27	7.684%	$140.2799	$140.28	$140.30	$140.30
Purchase #3	$153.95	5.843%	$162.9453	$162.95	$162.95	$162.90
Purchase #4	$96.38	12.328%	$108.2617	$108.26	$108.25	$108.30
Purchase #5	$184.69	13.460%	$209.5493	$209.55	$209.55	$209.50
Purchase #6	$161.96	13.811%	$184.3283	$184.33	$184.35	$184.30
Purchase #7	$55.50	11.149%	$61.6877	$61.69	$61.70	$61.70
7 purchase totals =	$842.16		$929.9430	$929.95	$930.00	$929.90