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	$67.27	7.368%	$72.2265	$72.23	$72.25	$72.20
Purchase #2	$167.31	10.130%	$184.2585	$184.26	$184.25	$184.30
Purchase #3	$147.47	9.123%	$160.9237	$160.92	$160.90	$160.90
Purchase #4	$13.43	12.801%	$15.1492	$15.15	$15.15	$15.10
Purchase #5	$96.34	4.296%	$100.4788	$100.48	$100.50	$100.50
Purchase #6	$141.53	3.475%	$146.4482	$146.45	$146.45	$146.40
Purchase #7	$184.69	10.478%	$204.0418	$204.04	$204.05	$204.00
7 purchase totals =	$818.04		$883.5267	$883.53	$883.55	$883.40