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	$200.97	5.259%	$211.539	$211.54	$211.55	$211.50
Purchase #2	$185.32	7.733%	$199.6508	$199.65	$199.65	$199.70
Purchase #3	$129.96	6.171%	$137.9798	$137.98	$138.00	$138.00
Purchase #4	$50.61	9.639%	$55.4883	$55.49	$55.50	$55.50
Purchase #5	$99.31	12.419%	$111.6433	$111.64	$111.65	$111.60
Purchase #6	$76.80	12.193%	$86.1642	$86.16	$86.15	$86.20
Purchase #7	$30.80	8.445%	$33.4011	$33.40	$33.40	$33.40
7 purchase totals =	$773.77		$835.8665	$835.86	$835.90	$835.90