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	$87.78	4.632%	$91.846	$91.85	$91.85	$91.80
Purchase #2	$174.37	6.202%	$185.1844	$185.18	$185.20	$185.20
Purchase #3	$160.52	3.350%	$165.8974	$165.90	$165.90	$165.90
Purchase #4	$197.55	10.739%	$218.7649	$218.76	$218.75	$218.80
Purchase #5	$69.40	13.262%	$78.6038	$78.60	$78.60	$78.60
Purchase #6	$188.97	11.385%	$210.4842	$210.48	$210.50	$210.50
Purchase #7	$114.79	3.790%	$119.1405	$119.14	$119.15	$119.10
7 purchase totals =	$993.38		$1,069.9212	$1,069.91	$1,069.95	$1,069.90