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	$97.96	11.731%	$109.4517	$109.45	$109.45	$109.50
Purchase #2	$129.93	12.496%	$146.1661	$146.17	$146.15	$146.20
Purchase #3	$197.33	9.795%	$216.6585	$216.66	$216.65	$216.70
Purchase #4	$97.92	6.738%	$104.5178	$104.52	$104.50	$104.50
Purchase #5	$75.78	7.407%	$81.393	$81.39	$81.40	$81.40
Purchase #6	$119.58	3.577%	$123.8574	$123.86	$123.85	$123.90
Purchase #7	$214.57	12.244%	$240.842	$240.84	$240.85	$240.80
7 purchase totals =	$933.07		$1,022.8865	$1,022.89	$1,022.85	$1,023.00