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	$151.97	6.515%	$161.8708	$161.87	$161.85	$161.90
Purchase #2	$172.35	11.799%	$192.6856	$192.69	$192.70	$192.70
Purchase #3	$95.90	6.584%	$102.2141	$102.21	$102.20	$102.20
Purchase #4	$115.96	13.700%	$131.8465	$131.85	$131.85	$131.80
Purchase #5	$26.93	7.122%	$28.848	$28.85	$28.85	$28.80
Purchase #6	$33.49	12.353%	$37.627	$37.63	$37.65	$37.60
Purchase #7	$118.67	10.693%	$131.3594	$131.36	$131.35	$131.40
7 purchase totals =	$715.27		$786.4514	$786.46	$786.45	$786.40