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	$42.83	7.332%	$45.9703	$45.97	$45.95	$46.00
Purchase #2	$144.25	12.639%	$162.4818	$162.48	$162.50	$162.50
Purchase #3	$147.79	13.289%	$167.4298	$167.43	$167.45	$167.40
Purchase #4	$222.55	8.575%	$241.6337	$241.63	$241.65	$241.60
Purchase #5	$167.90	6.283%	$178.4492	$178.45	$178.45	$178.40
Purchase #6	$33.76	11.688%	$37.7059	$37.71	$37.70	$37.70
Purchase #7	$241.93	12.514%	$272.2051	$272.21	$272.20	$272.20
7 purchase totals =	$1,001.01		$1,105.8758	$1,105.88	$1,105.90	$1,105.80