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	$163.79	13.356%	$185.6658	$185.67	$185.65	$185.70
Purchase #2	$19.90	3.164%	$20.5296	$20.53	$20.55	$20.50
Purchase #3	$33.38	9.171%	$36.4413	$36.44	$36.45	$36.40
Purchase #4	$115.82	13.481%	$131.4337	$131.43	$131.45	$131.40
Purchase #5	$90.72	13.471%	$102.9409	$102.94	$102.95	$102.90
Purchase #6	$76.80	9.327%	$83.9631	$83.96	$83.95	$84.00
Purchase #7	$82.91	13.341%	$93.971	$93.97	$93.95	$94.00
7 purchase totals =	$583.32		$654.9454	$654.94	$654.95	$654.90