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	$132.84	7.323%	$142.5679	$142.57	$142.55	$142.60
Purchase #2	$71.85	13.306%	$81.4104	$81.41	$81.40	$81.40
Purchase #3	$51.51	5.709%	$54.4507	$54.45	$54.45	$54.50
Purchase #4	$192.51	11.409%	$214.4735	$214.47	$214.45	$214.50
Purchase #5	$203.56	9.167%	$222.2203	$222.22	$222.20	$222.20
Purchase #6	$141.79	7.566%	$152.5178	$152.52	$152.50	$152.50
Purchase #7	$26.77	4.656%	$28.0164	$28.02	$28.00	$28.00
7 purchase totals =	$820.83		$895.6570	$895.66	$895.55	$895.70