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	$191.61	9.335%	$209.4968	$209.50	$209.50	$209.50
Purchase #2	$238.99	12.489%	$268.8375	$268.84	$268.85	$268.80
Purchase #3	$70.54	11.253%	$78.4779	$78.48	$78.50	$78.50
Purchase #4	$185.40	7.738%	$199.7463	$199.75	$199.75	$199.70
Purchase #5	$21.44	8.340%	$23.2281	$23.23	$23.25	$23.20
Purchase #6	$158.42	7.208%	$169.8389	$169.84	$169.85	$169.80
Purchase #7	$76.48	3.157%	$78.8945	$78.89	$78.90	$78.90
7 purchase totals =	$942.88		$1,028.5200	$1,028.53	$1,028.60	$1,028.40