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	$150.29	11.833%	$168.0738	$168.07	$168.05	$168.10
Purchase #2	$211.45	5.162%	$222.365	$222.37	$222.35	$222.40
Purchase #3	$28.38	6.232%	$30.1486	$30.15	$30.15	$30.10
Purchase #4	$137.64	11.527%	$153.5058	$153.51	$153.50	$153.50
Purchase #5	$112.71	12.400%	$126.686	$126.69	$126.70	$126.70
Purchase #6	$31.50	9.648%	$34.5391	$34.54	$34.55	$34.50
Purchase #7	$27.72	11.561%	$30.9247	$30.92	$30.90	$30.90
7 purchase totals =	$699.69		$766.2430	$766.25	$766.20	$766.20