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	$32.68	9.579%	$35.8104	$35.81	$35.80	$35.80
Purchase #2	$40.96	11.460%	$45.654	$45.65	$45.65	$45.70
Purchase #3	$21.96	11.815%	$24.5546	$24.55	$24.55	$24.60
Purchase #4	$214.91	8.654%	$233.5083	$233.51	$233.50	$233.50
Purchase #5	$243.40	4.288%	$253.837	$253.84	$253.85	$253.80
Purchase #6	$99.57	3.766%	$103.3198	$103.32	$103.30	$103.30
Purchase #7	$41.81	4.779%	$43.8081	$43.81	$43.80	$43.80
7 purchase totals =	$695.29		$740.4922	$740.49	$740.45	$740.50