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	$155.33	9.400%	$169.931	$169.93	$169.95	$169.90
Purchase #2	$53.68	3.593%	$55.6087	$55.61	$55.60	$55.60
Purchase #3	$146.25	10.700%	$161.8988	$161.90	$161.90	$161.90
Purchase #4	$124.86	5.583%	$131.8309	$131.83	$131.85	$131.80
Purchase #5	$202.42	7.423%	$217.4456	$217.45	$217.45	$217.40
Purchase #6	$211.70	3.870%	$219.8928	$219.89	$219.90	$219.90
Purchase #7	$135.80	5.743%	$143.599	$143.60	$143.60	$143.60
7 purchase totals =	$1,030.04		$1,100.2068	$1,100.21	$1,100.25	$1,100.10