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	$135.95	4.664%	$142.2907	$142.29	$142.30	$142.30
Purchase #2	$24.60	4.227%	$25.6398	$25.64	$25.65	$25.60
Purchase #3	$124.56	13.542%	$141.4279	$141.43	$141.45	$141.40
Purchase #4	$142.88	6.735%	$152.503	$152.50	$152.50	$152.50
Purchase #5	$92.97	3.820%	$96.5215	$96.52	$96.50	$96.50
Purchase #6	$221.73	13.854%	$252.4485	$252.45	$252.45	$252.40
Purchase #7	$37.43	8.613%	$40.6538	$40.65	$40.65	$40.70
7 purchase totals =	$780.12		$851.4852	$851.48	$851.50	$851.40