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	$78.83	8.356%	$85.417	$85.42	$85.40	$85.40
Purchase #2	$221.79	6.303%	$235.7694	$235.77	$235.75	$235.80
Purchase #3	$166.33	5.484%	$175.4515	$175.45	$175.45	$175.50
Purchase #4	$211.41	9.490%	$231.4728	$231.47	$231.45	$231.50
Purchase #5	$90.31	13.449%	$102.4558	$102.46	$102.45	$102.50
Purchase #6	$157.83	8.817%	$171.7459	$171.75	$171.75	$171.70
Purchase #7	$245.52	5.806%	$259.7749	$259.77	$259.75	$259.80
7 purchase totals =	$1,172.02		$1,262.0873	$1,262.09	$1,262.00	$1,262.20