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	$239.59	3.223%	$247.312	$247.31	$247.30	$247.30
Purchase #2	$76.33	11.483%	$85.095	$85.10	$85.10	$85.10
Purchase #3	$112.43	10.256%	$123.9608	$123.96	$123.95	$124.00
Purchase #4	$98.25	13.315%	$111.332	$111.33	$111.35	$111.30
Purchase #5	$172.56	13.468%	$195.8004	$195.80	$195.80	$195.80
Purchase #6	$134.96	11.670%	$150.7098	$150.71	$150.70	$150.70
Purchase #7	$164.51	3.385%	$170.0787	$170.08	$170.10	$170.10
7 purchase totals =	$998.63		$1,084.2887	$1,084.29	$1,084.30	$1,084.30