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	$235.30	3.467%	$243.4579	$243.46	$243.45	$243.50
Purchase #2	$93.50	7.310%	$100.3349	$100.33	$100.35	$100.30
Purchase #3	$109.55	7.590%	$117.8648	$117.86	$117.85	$117.90
Purchase #4	$45.89	7.825%	$49.4809	$49.48	$49.50	$49.50
Purchase #5	$233.36	13.197%	$264.1565	$264.16	$264.15	$264.20
Purchase #6	$119.88	6.817%	$128.0522	$128.05	$128.05	$128.10
Purchase #7	$37.90	4.273%	$39.5195	$39.52	$39.50	$39.50
7 purchase totals =	$875.38		$942.8667	$942.86	$942.85	$943.00