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	$227.64	3.314%	$235.184	$235.18	$235.20	$235.20
Purchase #2	$134.93	5.498%	$142.3485	$142.35	$142.35	$142.30
Purchase #3	$37.43	7.801%	$40.3499	$40.35	$40.35	$40.30
Purchase #4	$212.69	6.164%	$225.8002	$225.80	$225.80	$225.80
Purchase #5	$212.51	3.216%	$219.3443	$219.34	$219.35	$219.30
Purchase #6	$60.79	10.338%	$67.0745	$67.07	$67.05	$67.10
Purchase #7	$100.45	3.705%	$104.1717	$104.17	$104.15	$104.20
7 purchase totals =	$986.44		$1,034.2731	$1,034.26	$1,034.25	$1,034.20