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	$181.31	10.110%	$199.6404	$199.64	$199.65	$199.60
Purchase #2	$149.83	10.439%	$165.4708	$165.47	$165.45	$165.50
Purchase #3	$250.86	10.749%	$277.8249	$277.82	$277.80	$277.80
Purchase #4	$94.70	10.202%	$104.3613	$104.36	$104.35	$104.40
Purchase #5	$160.77	8.514%	$174.458	$174.46	$174.45	$174.50
Purchase #6	$219.25	3.681%	$227.3206	$227.32	$227.30	$227.30
Purchase #7	$80.50	4.208%	$83.8874	$83.89	$83.90	$83.90
7 purchase totals =	$1,137.22		$1,232.9634	$1,232.96	$1,232.90	$1,233.00