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	$86.38	10.118%	$95.1199	$95.12	$95.10	$95.10
Purchase #2	$190.53	13.568%	$216.3811	$216.38	$216.40	$216.40
Purchase #3	$116.44	10.724%	$128.927	$128.93	$128.95	$128.90
Purchase #4	$125.59	9.800%	$137.8978	$137.90	$137.90	$137.90
Purchase #5	$6.76	5.742%	$7.1482	$7.15	$7.15	$7.10
Purchase #6	$115.44	13.195%	$130.6723	$130.67	$130.65	$130.70
Purchase #7	$27.41	3.836%	$28.4614	$28.46	$28.45	$28.50
7 purchase totals =	$668.55		$744.6077	$744.61	$744.60	$744.60