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	$190.56	5.203%	$200.4748	$200.47	$200.45	$200.50
Purchase #2	$145.60	10.357%	$160.6798	$160.68	$160.70	$160.70
Purchase #3	$194.56	9.208%	$212.4751	$212.48	$212.50	$212.50
Purchase #4	$120.43	13.279%	$136.4219	$136.42	$136.40	$136.40
Purchase #5	$219.74	7.602%	$236.4446	$236.44	$236.45	$236.40
Purchase #6	$138.33	11.419%	$154.1259	$154.13	$154.15	$154.10
Purchase #7	$185.34	8.375%	$200.8622	$200.86	$200.85	$200.90
7 purchase totals =	$1,194.56		$1,301.4843	$1,301.48	$1,301.50	$1,301.50