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	$36.69	3.713%	$38.0523	$38.05	$38.05	$38.10
Purchase #2	$133.60	12.621%	$150.4617	$150.46	$150.45	$150.50
Purchase #3	$209.70	6.417%	$223.1564	$223.16	$223.15	$223.20
Purchase #4	$30.63	7.303%	$32.8669	$32.87	$32.85	$32.90
Purchase #5	$175.87	3.484%	$181.9973	$182.00	$182.00	$182.00
Purchase #6	$232.53	12.863%	$262.4403	$262.44	$262.45	$262.40
Purchase #7	$58.54	11.602%	$65.3318	$65.33	$65.35	$65.30
7 purchase totals =	$877.56		$954.3067	$954.31	$954.30	$954.40