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	$35.78	7.610%	$38.5029	$38.50	$38.50	$38.50
Purchase #2	$151.50	7.580%	$162.9837	$162.98	$163.00	$163.00
Purchase #3	$123.70	7.206%	$132.6138	$132.61	$132.60	$132.60
Purchase #4	$59.67	7.455%	$64.1184	$64.12	$64.10	$64.10
Purchase #5	$61.68	7.816%	$66.5009	$66.50	$66.50	$66.50
Purchase #6	$157.38	11.568%	$175.5857	$175.59	$175.60	$175.60
Purchase #7	$57.80	13.388%	$65.5383	$65.54	$65.55	$65.50
7 purchase totals =	$647.51		$705.8437	$705.84	$705.85	$705.80