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	$201.67	10.442%	$222.7284	$222.73	$222.75	$222.70
Purchase #2	$161.64	3.862%	$167.8825	$167.88	$167.90	$167.90
Purchase #3	$143.80	4.673%	$150.5198	$150.52	$150.50	$150.50
Purchase #4	$125.27	6.773%	$133.7545	$133.75	$133.75	$133.80
Purchase #5	$106.72	10.659%	$118.0953	$118.10	$118.10	$118.10
Purchase #6	$228.48	8.504%	$247.9099	$247.91	$247.90	$247.90
Purchase #7	$40.60	11.749%	$45.3701	$45.37	$45.35	$45.40
7 purchase totals =	$1,008.18		$1,086.2605	$1,086.26	$1,086.25	$1,086.30