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	$163.38	9.146%	$178.3227	$178.32	$178.30	$178.30
Purchase #2	$28.57	12.150%	$32.0413	$32.04	$32.05	$32.00
Purchase #3	$11.26	4.507%	$11.7675	$11.77	$11.75	$11.80
Purchase #4	$104.71	11.262%	$116.5024	$116.50	$116.50	$116.50
Purchase #5	$40.38	5.693%	$42.6788	$42.68	$42.70	$42.70
Purchase #6	$161.28	13.379%	$182.8577	$182.86	$182.85	$182.90
Purchase #7	$35.77	4.581%	$37.4086	$37.41	$37.40	$37.40
7 purchase totals =	$545.35		$601.5790	$601.58	$601.55	$601.60