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	$101.34	12.264%	$113.7683	$113.77	$113.75	$113.80
Purchase #2	$143.98	5.748%	$152.256	$152.26	$152.25	$152.30
Purchase #3	$137.58	9.600%	$150.7877	$150.79	$150.80	$150.80
Purchase #4	$249.61	7.204%	$267.5919	$267.59	$267.60	$267.60
Purchase #5	$202.90	5.755%	$214.5769	$214.58	$214.60	$214.60
Purchase #6	$74.33	12.723%	$83.787	$83.79	$83.80	$83.80
Purchase #7	$40.53	4.497%	$42.3526	$42.35	$42.35	$42.40
7 purchase totals =	$950.27		$1,025.1204	$1,025.13	$1,025.15	$1,025.30