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	$164.88	11.528%	$183.8874	$183.89	$183.90	$183.90
Purchase #2	$129.45	9.865%	$142.2202	$142.22	$142.20	$142.20
Purchase #3	$242.69	13.260%	$274.8707	$274.87	$274.85	$274.90
Purchase #4	$175.86	6.237%	$186.8284	$186.83	$186.85	$186.80
Purchase #5	$91.78	9.482%	$100.4826	$100.48	$100.50	$100.50
Purchase #6	$143.42	6.583%	$152.8613	$152.86	$152.85	$152.90
Purchase #7	$48.43	11.401%	$53.9515	$53.95	$53.95	$54.00
7 purchase totals =	$996.51		$1,095.1021	$1,095.10	$1,095.10	$1,095.20