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	$146.41	3.551%	$151.609	$151.61	$151.60	$151.60
Purchase #2	$87.88	3.102%	$90.606	$90.61	$90.60	$90.60
Purchase #3	$75.40	12.719%	$84.9901	$84.99	$85.00	$85.00
Purchase #4	$137.67	12.176%	$154.4327	$154.43	$154.45	$154.40
Purchase #5	$245.39	7.730%	$264.3586	$264.36	$264.35	$264.40
Purchase #6	$63.66	6.300%	$67.6706	$67.67	$67.65	$67.70
Purchase #7	$224.44	4.642%	$234.8585	$234.86	$234.85	$234.90
7 purchase totals =	$980.85		$1,048.5255	$1,048.53	$1,048.50	$1,048.60