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	$37.50	3.164%	$38.6865	$38.69	$38.70	$38.70
Purchase #2	$48.25	5.401%	$50.856	$50.86	$50.85	$50.90
Purchase #3	$102.74	13.148%	$116.2483	$116.25	$116.25	$116.20
Purchase #4	$187.40	12.263%	$210.3809	$210.38	$210.40	$210.40
Purchase #5	$85.80	10.312%	$94.6477	$94.65	$94.65	$94.60
Purchase #6	$177.54	3.704%	$184.1161	$184.12	$184.10	$184.10
Purchase #7	$43.96	3.491%	$45.4946	$45.49	$45.50	$45.50
7 purchase totals =	$683.19		$740.4301	$740.44	$740.45	$740.40