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	$217.32	7.445%	$233.4995	$233.50	$233.50	$233.50
Purchase #2	$169.45	11.746%	$189.3536	$189.35	$189.35	$189.40
Purchase #3	$162.75	6.570%	$173.4427	$173.44	$173.45	$173.40
Purchase #4	$45.73	8.455%	$49.5965	$49.60	$49.60	$49.60
Purchase #5	$40.41	5.426%	$42.6026	$42.60	$42.60	$42.60
Purchase #6	$17.57	10.139%	$19.3514	$19.35	$19.35	$19.40
Purchase #7	$126.46	11.586%	$141.1117	$141.11	$141.10	$141.10
7 purchase totals =	$779.69		$848.9580	$848.95	$848.95	$849.00