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	$199.41	10.141%	$219.6322	$219.63	$219.65	$219.60
Purchase #2	$19.49	6.445%	$20.7461	$20.75	$20.75	$20.70
Purchase #3	$118.86	12.331%	$133.5166	$133.52	$133.50	$133.50
Purchase #4	$126.66	7.556%	$136.2304	$136.23	$136.25	$136.20
Purchase #5	$65.77	9.723%	$72.1648	$72.16	$72.15	$72.20
Purchase #6	$67.58	3.742%	$70.1088	$70.11	$70.10	$70.10
Purchase #7	$87.28	13.795%	$99.3203	$99.32	$99.30	$99.30
7 purchase totals =	$685.05		$751.7192	$751.72	$751.70	$751.60