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	$179.41	11.267%	$199.6241	$199.62	$199.60	$199.60
Purchase #2	$232.42	10.443%	$256.6916	$256.69	$256.70	$256.70
Purchase #3	$226.90	5.867%	$240.2122	$240.21	$240.20	$240.20
Purchase #4	$148.72	10.475%	$164.2984	$164.30	$164.30	$164.30
Purchase #5	$95.62	8.145%	$103.4082	$103.41	$103.40	$103.40
Purchase #6	$95.71	3.869%	$99.413	$99.41	$99.40	$99.40
Purchase #7	$61.76	12.326%	$69.3725	$69.37	$69.35	$69.40
7 purchase totals =	$1,040.54		$1,133.0200	$1,133.01	$1,132.95	$1,133.00