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	$206.55	6.446%	$219.8642	$219.86	$219.85	$219.90
Purchase #2	$113.47	11.489%	$126.5066	$126.51	$126.50	$126.50
Purchase #3	$240.79	5.740%	$254.6113	$254.61	$254.60	$254.60
Purchase #4	$93.85	6.704%	$100.1417	$100.14	$100.15	$100.10
Purchase #5	$102.67	3.761%	$106.5314	$106.53	$106.55	$106.50
Purchase #6	$50.32	10.513%	$55.6101	$55.61	$55.60	$55.60
Purchase #7	$75.57	9.471%	$82.7272	$82.73	$82.75	$82.70
7 purchase totals =	$883.22		$945.9925	$945.99	$946.00	$945.90