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	$108.45	13.810%	$123.4269	$123.43	$123.45	$123.40
Purchase #2	$187.78	11.684%	$209.7202	$209.72	$209.70	$209.70
Purchase #3	$28.61	12.594%	$32.2131	$32.21	$32.20	$32.20
Purchase #4	$155.46	12.569%	$174.9998	$175.00	$175.00	$175.00
Purchase #5	$60.84	11.161%	$67.6304	$67.63	$67.65	$67.60
Purchase #6	$222.48	8.245%	$240.8235	$240.82	$240.80	$240.80
Purchase #7	$160.43	6.738%	$171.2398	$171.24	$171.25	$171.20
7 purchase totals =	$924.05		$1,020.0537	$1,020.05	$1,020.05	$1,019.90