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	$47.57	7.763%	$51.2629	$51.26	$51.25	$51.30
Purchase #2	$95.91	3.809%	$99.5632	$99.56	$99.55	$99.60
Purchase #3	$136.51	10.775%	$151.219	$151.22	$151.20	$151.20
Purchase #4	$78.50	13.751%	$89.2945	$89.29	$89.30	$89.30
Purchase #5	$113.70	11.612%	$126.9028	$126.90	$126.90	$126.90
Purchase #6	$214.94	5.589%	$226.953	$226.95	$226.95	$227.00
Purchase #7	$49.43	4.275%	$51.5431	$51.54	$51.55	$51.50
7 purchase totals =	$736.56		$796.7385	$796.72	$796.70	$796.80