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	$190.88	11.803%	$213.4096	$213.41	$213.40	$213.40
Purchase #2	$63.61	12.126%	$71.3233	$71.32	$71.30	$71.30
Purchase #3	$96.75	4.325%	$100.9344	$100.93	$100.95	$100.90
Purchase #4	$96.85	4.420%	$101.1308	$101.13	$101.15	$101.10
Purchase #5	$59.46	10.313%	$65.5921	$65.59	$65.60	$65.60
Purchase #6	$177.85	6.341%	$189.1275	$189.13	$189.15	$189.10
Purchase #7	$219.52	7.653%	$236.3199	$236.32	$236.30	$236.30
7 purchase totals =	$904.92		$977.8376	$977.83	$977.85	$977.70