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	$243.29	7.348%	$261.1669	$261.17	$261.15	$261.20
Purchase #2	$73.53	13.648%	$83.5654	$83.57	$83.55	$83.60
Purchase #3	$126.97	12.264%	$142.5416	$142.54	$142.55	$142.50
Purchase #4	$245.83	4.242%	$256.2581	$256.26	$256.25	$256.30
Purchase #5	$214.62	12.694%	$241.8639	$241.86	$241.85	$241.90
Purchase #6	$78.29	9.482%	$85.7135	$85.71	$85.70	$85.70
Purchase #7	$52.62	5.337%	$55.4283	$55.43	$55.45	$55.40
7 purchase totals =	$1,035.15		$1,126.5377	$1,126.54	$1,126.50	$1,126.60