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	$163.93	9.480%	$179.4706	$179.47	$179.45	$179.50
Purchase #2	$157.65	8.142%	$170.4859	$170.49	$170.50	$170.50
Purchase #3	$229.34	8.673%	$249.2307	$249.23	$249.25	$249.20
Purchase #4	$170.49	11.722%	$190.4748	$190.47	$190.45	$190.50
Purchase #5	$216.65	7.689%	$233.3082	$233.31	$233.30	$233.30
Purchase #6	$92.85	8.150%	$100.4173	$100.42	$100.40	$100.40
Purchase #7	$126.25	11.860%	$141.2233	$141.22	$141.20	$141.20
7 purchase totals =	$1,157.16		$1,264.6108	$1,264.61	$1,264.55	$1,264.60