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	$156.98	5.403%	$165.4616	$165.46	$165.45	$165.50
Purchase #2	$128.73	10.345%	$142.0471	$142.05	$142.05	$142.00
Purchase #3	$115.48	8.211%	$124.9621	$124.96	$124.95	$125.00
Purchase #4	$72.70	13.812%	$82.7413	$82.74	$82.75	$82.70
Purchase #5	$125.98	11.820%	$140.8708	$140.87	$140.85	$140.90
Purchase #6	$142.25	10.774%	$157.576	$157.58	$157.60	$157.60
Purchase #7	$125.35	5.121%	$131.7692	$131.77	$131.75	$131.80
7 purchase totals =	$867.47		$945.4281	$945.43	$945.40	$945.50