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	$7.55	6.847%	$8.0669	$8.07	$8.05	$8.10
Purchase #2	$35.57	5.377%	$37.4826	$37.48	$37.50	$37.50
Purchase #3	$81.58	3.529%	$84.459	$84.46	$84.45	$84.50
Purchase #4	$110.98	5.109%	$116.65	$116.65	$116.65	$116.70
Purchase #5	$41.97	3.168%	$43.2996	$43.30	$43.30	$43.30
Purchase #6	$92.54	8.474%	$100.3818	$100.38	$100.40	$100.40
Purchase #7	$88.51	13.741%	$100.6722	$100.67	$100.65	$100.70
7 purchase totals =	$458.70		$491.0121	$491.01	$491.00	$491.20