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	$63.29	13.499%	$71.8335	$71.83	$71.85	$71.80
Purchase #2	$206.89	11.464%	$230.6079	$230.61	$230.60	$230.60
Purchase #3	$18.97	8.263%	$20.5375	$20.54	$20.55	$20.50
Purchase #4	$177.55	13.672%	$201.8246	$201.82	$201.80	$201.80
Purchase #5	$89.80	12.231%	$100.7834	$100.78	$100.80	$100.80
Purchase #6	$19.74	4.441%	$20.6167	$20.62	$20.60	$20.60
Purchase #7	$154.77	3.308%	$159.8898	$159.89	$159.90	$159.90
7 purchase totals =	$731.01		$806.0934	$806.09	$806.10	$806.00