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	$198.46	13.614%	$225.4783	$225.48	$225.50	$225.50
Purchase #2	$189.56	13.472%	$215.0975	$215.10	$215.10	$215.10
Purchase #3	$70.69	8.771%	$76.8902	$76.89	$76.90	$76.90
Purchase #4	$152.57	5.188%	$160.4853	$160.49	$160.50	$160.50
Purchase #5	$72.72	8.493%	$78.8961	$78.90	$78.90	$78.90
Purchase #6	$45.47	8.764%	$49.455	$49.46	$49.45	$49.50
Purchase #7	$123.73	11.487%	$137.9429	$137.94	$137.95	$137.90
7 purchase totals =	$853.20		$944.2453	$944.26	$944.30	$944.30