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	$155.96	3.150%	$160.8727	$160.87	$160.85	$160.90
Purchase #2	$136.90	3.871%	$142.1994	$142.20	$142.20	$142.20
Purchase #3	$243.67	4.824%	$255.4246	$255.42	$255.40	$255.40
Purchase #4	$99.53	4.660%	$104.1681	$104.17	$104.15	$104.20
Purchase #5	$139.90	4.638%	$146.3886	$146.39	$146.40	$146.40
Purchase #6	$169.33	7.742%	$182.4395	$182.44	$182.45	$182.40
Purchase #7	$77.27	6.639%	$82.4	$82.40	$82.40	$82.40
7 purchase totals =	$1,022.56		$1,073.8929	$1,073.89	$1,073.85	$1,073.90