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	$162.38	13.586%	$184.4409	$184.44	$184.45	$184.40
Purchase #2	$71.31	11.426%	$79.4579	$79.46	$79.45	$79.50
Purchase #3	$223.29	10.655%	$247.0815	$247.08	$247.10	$247.10
Purchase #4	$26.59	7.121%	$28.4835	$28.48	$28.50	$28.50
Purchase #5	$127.31	11.149%	$141.5038	$141.50	$141.50	$141.50
Purchase #6	$196.68	12.558%	$221.3791	$221.38	$221.40	$221.40
Purchase #7	$155.97	8.721%	$169.5721	$169.57	$169.55	$169.60
7 purchase totals =	$963.53		$1,071.9188	$1,071.91	$1,071.95	$1,072.00