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	$227.80	13.611%	$258.8059	$258.81	$258.80	$258.80
Purchase #2	$249.75	10.469%	$275.8963	$275.90	$275.90	$275.90
Purchase #3	$236.87	5.597%	$250.1276	$250.13	$250.15	$250.10
Purchase #4	$181.75	8.376%	$196.9734	$196.97	$196.95	$197.00
Purchase #5	$165.57	11.164%	$184.0542	$184.05	$184.05	$184.10
Purchase #6	$210.85	5.660%	$222.7841	$222.78	$222.80	$222.80
Purchase #7	$223.37	8.678%	$242.754	$242.75	$242.75	$242.80
7 purchase totals =	$1,495.96		$1,631.3955	$1,631.39	$1,631.40	$1,631.50