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	$140.72	5.418%	$148.3442	$148.34	$148.35	$148.30
Purchase #2	$141.82	6.820%	$151.4921	$151.49	$151.50	$151.50
Purchase #3	$146.26	12.342%	$164.3114	$164.31	$164.30	$164.30
Purchase #4	$13.34	4.171%	$13.8964	$13.90	$13.90	$13.90
Purchase #5	$161.40	5.315%	$169.9784	$169.98	$170.00	$170.00
Purchase #6	$177.44	12.430%	$199.4958	$199.50	$199.50	$199.50
Purchase #7	$200.62	9.610%	$219.8996	$219.90	$219.90	$219.90
7 purchase totals =	$981.60		$1,067.4179	$1,067.42	$1,067.45	$1,067.40