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	$165.63	10.330%	$182.7396	$182.74	$182.75	$182.70
Purchase #2	$136.57	11.855%	$152.7604	$152.76	$152.75	$152.80
Purchase #3	$125.89	13.726%	$143.1697	$143.17	$143.15	$143.20
Purchase #4	$175.68	13.838%	$199.9906	$199.99	$200.00	$200.00
Purchase #5	$166.74	3.186%	$172.0523	$172.05	$172.05	$172.10
Purchase #6	$217.25	5.186%	$228.5166	$228.52	$228.50	$228.50
Purchase #7	$94.85	4.705%	$99.3127	$99.31	$99.30	$99.30
7 purchase totals =	$1,082.61		$1,178.5419	$1,178.54	$1,178.50	$1,178.60