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	$189.70	10.371%	$209.3738	$209.37	$209.35	$209.40
Purchase #2	$9.72	11.242%	$10.8127	$10.81	$10.80	$10.80
Purchase #3	$79.49	3.799%	$82.5098	$82.51	$82.50	$82.50
Purchase #4	$187.42	7.434%	$201.3528	$201.35	$201.35	$201.40
Purchase #5	$216.25	13.656%	$245.7811	$245.78	$245.80	$245.80
Purchase #6	$147.82	8.815%	$160.8503	$160.85	$160.85	$160.90
Purchase #7	$94.76	5.691%	$100.1528	$100.15	$100.15	$100.20
7 purchase totals =	$925.16		$1,010.8333	$1,010.82	$1,010.80	$1,011.00