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	$130.49	10.470%	$144.1523	$144.15	$144.15	$144.20
Purchase #2	$139.83	6.302%	$148.6421	$148.64	$148.65	$148.60
Purchase #3	$221.38	9.548%	$242.5174	$242.52	$242.50	$242.50
Purchase #4	$133.34	6.594%	$142.1324	$142.13	$142.15	$142.10
Purchase #5	$241.29	11.642%	$269.381	$269.38	$269.40	$269.40
Purchase #6	$29.42	12.612%	$33.1305	$33.13	$33.15	$33.10
Purchase #7	$64.53	12.768%	$72.7692	$72.77	$72.75	$72.80
7 purchase totals =	$960.28		$1,052.7249	$1,052.72	$1,052.75	$1,052.70