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	$119.58	7.224%	$128.2185	$128.22	$128.20	$128.20
Purchase #2	$64.27	10.231%	$70.8455	$70.85	$70.85	$70.80
Purchase #3	$6.98	10.400%	$7.7059	$7.71	$7.70	$7.70
Purchase #4	$241.44	10.588%	$267.0037	$267.00	$267.00	$267.00
Purchase #5	$16.31	9.679%	$17.8886	$17.89	$17.90	$17.90
Purchase #6	$31.90	6.257%	$33.896	$33.90	$33.90	$33.90
Purchase #7	$179.89	9.180%	$196.4039	$196.40	$196.40	$196.40
7 purchase totals =	$660.37		$721.9621	$721.97	$721.95	$721.90