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	$199.89	6.404%	$212.691	$212.69	$212.70	$212.70
Purchase #2	$220.80	3.648%	$228.8548	$228.85	$228.85	$228.90
Purchase #3	$206.83	3.308%	$213.6719	$213.67	$213.65	$213.70
Purchase #4	$57.35	13.444%	$65.0601	$65.06	$65.05	$65.10
Purchase #5	$157.38	5.463%	$165.9777	$165.98	$166.00	$166.00
Purchase #6	$85.92	5.305%	$90.4781	$90.48	$90.50	$90.50
Purchase #7	$170.86	10.651%	$189.0583	$189.06	$189.05	$189.10
7 purchase totals =	$1,099.03		$1,165.7919	$1,165.79	$1,165.80	$1,166.00