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	$81.67	4.661%	$85.4766	$85.48	$85.50	$85.50
Purchase #2	$232.51	6.493%	$247.6069	$247.61	$247.60	$247.60
Purchase #3	$54.80	12.755%	$61.7897	$61.79	$61.80	$61.80
Purchase #4	$38.44	11.452%	$42.8421	$42.84	$42.85	$42.80
Purchase #5	$238.80	7.216%	$256.0318	$256.03	$256.05	$256.00
Purchase #6	$139.30	3.294%	$143.8885	$143.89	$143.90	$143.90
Purchase #7	$182.95	3.725%	$189.7649	$189.76	$189.75	$189.80
7 purchase totals =	$968.47		$1,027.4005	$1,027.40	$1,027.45	$1,027.40