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	$172.54	7.639%	$185.7203	$185.72	$185.70	$185.70
Purchase #2	$166.94	10.541%	$184.5371	$184.54	$184.55	$184.50
Purchase #3	$53.75	4.212%	$56.014	$56.01	$56.00	$56.00
Purchase #4	$131.65	7.537%	$141.5725	$141.57	$141.55	$141.60
Purchase #5	$137.43	3.762%	$142.6001	$142.60	$142.60	$142.60
Purchase #6	$13.48	12.208%	$15.1256	$15.13	$15.15	$15.10
Purchase #7	$26.42	7.280%	$28.3434	$28.34	$28.35	$28.30
7 purchase totals =	$702.21		$753.9130	$753.91	$753.90	$753.80