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	$117.95	8.771%	$128.2954	$128.30	$128.30	$128.30
Purchase #2	$219.35	10.557%	$242.5068	$242.51	$242.50	$242.50
Purchase #3	$78.29	9.647%	$85.8426	$85.84	$85.85	$85.80
Purchase #4	$32.70	3.633%	$33.888	$33.89	$33.90	$33.90
Purchase #5	$244.95	11.484%	$273.0801	$273.08	$273.10	$273.10
Purchase #6	$32.54	7.109%	$34.8533	$34.85	$34.85	$34.90
Purchase #7	$196.30	13.315%	$222.4373	$222.44	$222.45	$222.40
7 purchase totals =	$922.08		$1,020.9035	$1,020.91	$1,020.95	$1,020.90