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	$234.43	4.710%	$245.4717	$245.47	$245.45	$245.50
Purchase #2	$129.30	6.130%	$137.2261	$137.23	$137.25	$137.20
Purchase #3	$95.82	11.445%	$106.7866	$106.79	$106.80	$106.80
Purchase #4	$71.89	9.666%	$78.8389	$78.84	$78.85	$78.80
Purchase #5	$25.48	12.242%	$28.5993	$28.60	$28.60	$28.60
Purchase #6	$239.66	8.555%	$260.1629	$260.16	$260.15	$260.20
Purchase #7	$206.34	7.596%	$222.0136	$222.01	$222.00	$222.00
7 purchase totals =	$1,002.92		$1,079.0991	$1,079.10	$1,079.10	$1,079.10