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	$196.32	4.108%	$204.3848	$204.38	$204.40	$204.40
Purchase #2	$86.82	13.437%	$98.486	$98.49	$98.50	$98.50
Purchase #3	$57.89	8.524%	$62.8245	$62.82	$62.80	$62.80
Purchase #4	$77.90	4.466%	$81.379	$81.38	$81.40	$81.40
Purchase #5	$184.92	11.130%	$205.5016	$205.50	$205.50	$205.50
Purchase #6	$121.98	12.500%	$137.2275	$137.23	$137.25	$137.20
Purchase #7	$234.95	10.541%	$259.7161	$259.72	$259.70	$259.70
7 purchase totals =	$960.78		$1,049.5195	$1,049.52	$1,049.55	$1,049.50