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	$165.84	12.431%	$186.4556	$186.46	$186.45	$186.50
Purchase #2	$47.57	4.792%	$49.8496	$49.85	$49.85	$49.80
Purchase #3	$85.40	13.331%	$96.7847	$96.78	$96.80	$96.80
Purchase #4	$78.86	6.738%	$84.1736	$84.17	$84.15	$84.20
Purchase #5	$92.57	7.290%	$99.3184	$99.32	$99.30	$99.30
Purchase #6	$94.52	8.813%	$102.85	$102.85	$102.85	$102.90
Purchase #7	$90.48	10.312%	$99.8103	$99.81	$99.80	$99.80
7 purchase totals =	$655.24		$719.2422	$719.24	$719.20	$719.30