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	$74.60	10.546%	$82.4673	$82.47	$82.45	$82.50
Purchase #2	$141.55	7.584%	$152.2852	$152.29	$152.30	$152.30
Purchase #3	$6.32	12.113%	$7.0855	$7.09	$7.10	$7.10
Purchase #4	$195.79	12.487%	$220.2383	$220.24	$220.25	$220.20
Purchase #5	$151.94	12.847%	$171.4597	$171.46	$171.45	$171.50
Purchase #6	$149.43	12.764%	$168.5032	$168.50	$168.50	$168.50
Purchase #7	$166.97	3.584%	$172.9542	$172.95	$172.95	$173.00
7 purchase totals =	$886.60		$974.9934	$975.00	$975.00	$975.10