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	$198.81	5.290%	$209.327	$209.33	$209.35	$209.30
Purchase #2	$95.95	4.813%	$100.5681	$100.57	$100.55	$100.60
Purchase #3	$19.51	6.367%	$20.7522	$20.75	$20.75	$20.80
Purchase #4	$115.42	3.840%	$119.8521	$119.85	$119.85	$119.90
Purchase #5	$84.58	6.344%	$89.9458	$89.95	$89.95	$89.90
Purchase #6	$205.62	5.164%	$216.2382	$216.24	$216.25	$216.20
Purchase #7	$89.58	4.808%	$93.887	$93.89	$93.90	$93.90
7 purchase totals =	$809.47		$850.5704	$850.58	$850.60	$850.60