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	$147.29	11.662%	$164.467	$164.47	$164.45	$164.50
Purchase #2	$18.26	12.771%	$20.592	$20.59	$20.60	$20.60
Purchase #3	$95.75	9.290%	$104.6452	$104.65	$104.65	$104.60
Purchase #4	$196.95	13.612%	$223.7588	$223.76	$223.75	$223.80
Purchase #5	$59.84	3.404%	$61.877	$61.88	$61.90	$61.90
Purchase #6	$224.57	8.325%	$243.2655	$243.27	$243.25	$243.30
Purchase #7	$66.33	12.214%	$74.4315	$74.43	$74.45	$74.40
7 purchase totals =	$808.99		$893.0370	$893.05	$893.05	$893.10