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	$127.44	7.457%	$136.9432	$136.94	$136.95	$136.90
Purchase #2	$217.31	7.683%	$234.0059	$234.01	$234.00	$234.00
Purchase #3	$241.37	11.813%	$269.883	$269.88	$269.90	$269.90
Purchase #4	$65.33	11.366%	$72.7554	$72.76	$72.75	$72.80
Purchase #5	$16.43	13.498%	$18.6477	$18.65	$18.65	$18.60
Purchase #6	$48.29	7.464%	$51.8944	$51.89	$51.90	$51.90
Purchase #7	$92.72	6.310%	$98.5706	$98.57	$98.55	$98.60
7 purchase totals =	$808.89		$882.7002	$882.70	$882.70	$882.70