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	$83.49	12.257%	$93.7234	$93.72	$93.70	$93.70
Purchase #2	$115.49	13.643%	$131.2463	$131.25	$131.25	$131.20
Purchase #3	$87.40	12.309%	$98.1581	$98.16	$98.15	$98.20
Purchase #4	$175.72	13.700%	$199.7936	$199.79	$199.80	$199.80
Purchase #5	$187.85	6.222%	$199.538	$199.54	$199.55	$199.50
Purchase #6	$122.98	7.142%	$131.7632	$131.76	$131.75	$131.80
Purchase #7	$245.68	4.735%	$257.3129	$257.31	$257.30	$257.30
7 purchase totals =	$1,018.61		$1,111.5355	$1,111.53	$1,111.50	$1,111.50