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	$63.74	6.497%	$67.8812	$67.88	$67.90	$67.90
Purchase #2	$86.64	3.766%	$89.9029	$89.90	$89.90	$89.90
Purchase #3	$231.67	13.380%	$262.6674	$262.67	$262.65	$262.70
Purchase #4	$203.82	4.109%	$212.195	$212.20	$212.20	$212.20
Purchase #5	$200.66	11.826%	$224.3901	$224.39	$224.40	$224.40
Purchase #6	$48.67	7.326%	$52.2356	$52.24	$52.25	$52.20
Purchase #7	$138.70	6.636%	$147.9041	$147.90	$147.90	$147.90
7 purchase totals =	$973.90		$1,057.1763	$1,057.18	$1,057.20	$1,057.20