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	$189.84	5.253%	$199.8123	$199.81	$199.80	$199.80
Purchase #2	$40.61	9.630%	$44.5207	$44.52	$44.50	$44.50
Purchase #3	$140.55	11.479%	$156.6837	$156.68	$156.70	$156.70
Purchase #4	$85.52	4.810%	$89.6335	$89.63	$89.65	$89.60
Purchase #5	$130.75	3.377%	$135.1654	$135.17	$135.15	$135.20
Purchase #6	$138.87	4.254%	$144.7775	$144.78	$144.80	$144.80
Purchase #7	$215.95	13.390%	$244.8657	$244.87	$244.85	$244.90
7 purchase totals =	$942.09		$1,015.4588	$1,015.46	$1,015.45	$1,015.50