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	$145.55	10.472%	$160.792	$160.79	$160.80	$160.80
Purchase #2	$195.36	11.113%	$217.0704	$217.07	$217.05	$217.10
Purchase #3	$89.90	6.218%	$95.49	$95.49	$95.50	$95.50
Purchase #4	$189.25	3.788%	$196.4188	$196.42	$196.40	$196.40
Purchase #5	$77.30	13.167%	$87.4781	$87.48	$87.50	$87.50
Purchase #6	$92.26	13.716%	$104.9144	$104.91	$104.90	$104.90
Purchase #7	$133.60	12.767%	$150.6567	$150.66	$150.65	$150.70
7 purchase totals =	$923.22		$1,012.8204	$1,012.82	$1,012.80	$1,012.90