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	$37.26	3.593%	$38.5988	$38.60	$38.60	$38.60
Purchase #2	$116.63	8.168%	$126.1563	$126.16	$126.15	$126.20
Purchase #3	$205.84	8.405%	$223.1409	$223.14	$223.15	$223.10
Purchase #4	$57.65	8.165%	$62.3571	$62.36	$62.35	$62.40
Purchase #5	$239.33	4.577%	$250.2841	$250.28	$250.30	$250.30
Purchase #6	$159.45	10.686%	$176.4888	$176.49	$176.50	$176.50
Purchase #7	$242.62	9.178%	$264.8877	$264.89	$264.90	$264.90
7 purchase totals =	$1,058.78		$1,141.9137	$1,141.92	$1,141.95	$1,142.00