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	$134.90	10.313%	$148.8122	$148.81	$148.80	$148.80
Purchase #2	$95.73	12.343%	$107.546	$107.55	$107.55	$107.50
Purchase #3	$39.44	8.290%	$42.7096	$42.71	$42.70	$42.70
Purchase #4	$137.56	4.361%	$143.559	$143.56	$143.55	$143.60
Purchase #5	$168.54	4.174%	$175.5749	$175.57	$175.55	$175.60
Purchase #6	$159.68	8.662%	$173.5115	$173.51	$173.50	$173.50
Purchase #7	$82.94	10.262%	$91.4513	$91.45	$91.45	$91.50
7 purchase totals =	$818.79		$883.1645	$883.16	$883.10	$883.20