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	$64.83	10.729%	$71.7856	$71.79	$71.80	$71.80
Purchase #2	$187.48	12.613%	$211.1269	$211.13	$211.15	$211.10
Purchase #3	$173.32	3.576%	$179.5179	$179.52	$179.50	$179.50
Purchase #4	$120.70	4.561%	$126.2051	$126.21	$126.20	$126.20
Purchase #5	$189.46	5.847%	$200.5377	$200.54	$200.55	$200.50
Purchase #6	$146.59	9.434%	$160.4193	$160.42	$160.40	$160.40
Purchase #7	$81.46	5.483%	$85.9265	$85.93	$85.95	$85.90
7 purchase totals =	$963.84		$1,035.5190	$1,035.54	$1,035.55	$1,035.40