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	$101.89	9.747%	$111.8212	$111.82	$111.80	$111.80
Purchase #2	$138.38	6.308%	$147.109	$147.11	$147.10	$147.10
Purchase #3	$226.35	12.379%	$254.3699	$254.37	$254.35	$254.40
Purchase #4	$65.69	12.559%	$73.94	$73.94	$73.95	$73.90
Purchase #5	$189.73	5.249%	$199.6889	$199.69	$199.70	$199.70
Purchase #6	$125.72	12.704%	$141.6915	$141.69	$141.70	$141.70
Purchase #7	$238.77	10.715%	$264.3542	$264.35	$264.35	$264.40
7 purchase totals =	$1,086.53		$1,192.9747	$1,192.97	$1,192.95	$1,193.00