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	$153.83	10.290%	$169.6591	$169.66	$169.65	$169.70
Purchase #2	$40.53	7.370%	$43.5171	$43.52	$43.50	$43.50
Purchase #3	$41.72	13.707%	$47.4386	$47.44	$47.45	$47.40
Purchase #4	$193.59	3.180%	$199.7462	$199.75	$199.75	$199.70
Purchase #5	$81.95	4.176%	$85.3722	$85.37	$85.35	$85.40
Purchase #6	$186.68	12.369%	$209.7704	$209.77	$209.75	$209.80
Purchase #7	$165.48	4.828%	$173.4694	$173.47	$173.45	$173.50
7 purchase totals =	$863.78		$928.9730	$928.98	$928.90	$929.00