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	$150.36	12.428%	$169.0467	$169.05	$169.05	$169.00
Purchase #2	$177.79	10.748%	$196.8989	$196.90	$196.90	$196.90
Purchase #3	$152.77	5.651%	$161.403	$161.40	$161.40	$161.40
Purchase #4	$171.75	9.527%	$188.1126	$188.11	$188.10	$188.10
Purchase #5	$159.72	3.748%	$165.7063	$165.71	$165.70	$165.70
Purchase #6	$107.36	3.106%	$110.6946	$110.69	$110.70	$110.70
Purchase #7	$22.57	10.412%	$24.92	$24.92	$24.90	$24.90
7 purchase totals =	$942.32		$1,016.7821	$1,016.78	$1,016.75	$1,016.70