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	$125.41	5.140%	$131.8561	$131.86	$131.85	$131.90
Purchase #2	$166.83	10.805%	$184.856	$184.86	$184.85	$184.90
Purchase #3	$13.69	11.438%	$15.2559	$15.26	$15.25	$15.30
Purchase #4	$48.26	4.326%	$50.3477	$50.35	$50.35	$50.30
Purchase #5	$90.53	11.372%	$100.8251	$100.83	$100.85	$100.80
Purchase #6	$219.41	9.618%	$240.5129	$240.51	$240.50	$240.50
Purchase #7	$217.53	8.857%	$236.7966	$236.80	$236.80	$236.80
7 purchase totals =	$881.66		$960.4503	$960.47	$960.45	$960.50