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	$190.86	4.302%	$199.0708	$199.07	$199.05	$199.10
Purchase #2	$77.68	6.293%	$82.5684	$82.57	$82.55	$82.60
Purchase #3	$6.92	12.836%	$7.8083	$7.81	$7.80	$7.80
Purchase #4	$80.98	4.467%	$84.5974	$84.60	$84.60	$84.60
Purchase #5	$18.95	13.240%	$21.459	$21.46	$21.45	$21.50
Purchase #6	$31.31	9.374%	$34.245	$34.25	$34.25	$34.20
Purchase #7	$79.73	12.115%	$89.3893	$89.39	$89.40	$89.40
7 purchase totals =	$486.43		$519.1382	$519.15	$519.10	$519.20