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	$148.93	12.371%	$167.3541	$167.35	$167.35	$167.40
Purchase #2	$227.27	11.337%	$253.0356	$253.04	$253.05	$253.00
Purchase #3	$132.69	9.199%	$144.8962	$144.90	$144.90	$144.90
Purchase #4	$147.40	10.543%	$162.9404	$162.94	$162.95	$162.90
Purchase #5	$229.45	3.161%	$236.7029	$236.70	$236.70	$236.70
Purchase #6	$70.43	3.122%	$72.6288	$72.63	$72.65	$72.60
Purchase #7	$50.95	7.408%	$54.7244	$54.72	$54.70	$54.70
7 purchase totals =	$1,007.12		$1,092.2824	$1,092.28	$1,092.30	$1,092.20