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	$224.77	7.354%	$241.2996	$241.30	$241.30	$241.30
Purchase #2	$160.43	12.778%	$180.9297	$180.93	$180.95	$180.90
Purchase #3	$238.78	5.413%	$251.7052	$251.71	$251.70	$251.70
Purchase #4	$52.91	12.212%	$59.3714	$59.37	$59.35	$59.40
Purchase #5	$248.26	13.651%	$282.15	$282.15	$282.15	$282.20
Purchase #6	$216.64	10.688%	$239.7945	$239.79	$239.80	$239.80
Purchase #7	$148.54	5.164%	$156.2106	$156.21	$156.20	$156.20
7 purchase totals =	$1,290.33		$1,411.4610	$1,411.46	$1,411.45	$1,411.50