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	$165.94	4.800%	$173.9051	$173.91	$173.90	$173.90
Purchase #2	$195.69	5.127%	$205.723	$205.72	$205.70	$205.70
Purchase #3	$213.93	3.868%	$222.2048	$222.20	$222.20	$222.20
Purchase #4	$241.94	4.107%	$251.8765	$251.88	$251.90	$251.90
Purchase #5	$62.64	8.387%	$67.8936	$67.89	$67.90	$67.90
Purchase #6	$18.43	6.532%	$19.6338	$19.63	$19.65	$19.60
Purchase #7	$104.97	11.185%	$116.7109	$116.71	$116.70	$116.70
7 purchase totals =	$1,003.54		$1,057.9477	$1,057.94	$1,057.95	$1,057.90