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	$67.80	3.336%	$70.0618	$70.06	$70.05	$70.10
Purchase #2	$244.77	3.564%	$253.4936	$253.49	$253.50	$253.50
Purchase #3	$41.35	10.287%	$45.6037	$45.60	$45.60	$45.60
Purchase #4	$233.51	9.708%	$256.1792	$256.18	$256.20	$256.20
Purchase #5	$159.65	6.143%	$169.4573	$169.46	$169.45	$169.50
Purchase #6	$224.98	4.316%	$234.6901	$234.69	$234.70	$234.70
Purchase #7	$171.48	9.331%	$187.4808	$187.48	$187.50	$187.50
7 purchase totals =	$1,143.54		$1,216.9665	$1,216.96	$1,217.00	$1,217.10