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	$20.48	11.245%	$22.783	$22.78	$22.80	$22.80
Purchase #2	$77.77	11.444%	$86.67	$86.67	$86.65	$86.70
Purchase #3	$117.65	11.618%	$131.3186	$131.32	$131.30	$131.30
Purchase #4	$68.25	5.555%	$72.0413	$72.04	$72.05	$72.00
Purchase #5	$91.70	4.229%	$95.578	$95.58	$95.60	$95.60
Purchase #6	$137.75	13.588%	$156.4675	$156.47	$156.45	$156.50
Purchase #7	$97.48	9.130%	$106.3799	$106.38	$106.40	$106.40
7 purchase totals =	$611.08		$671.2383	$671.24	$671.25	$671.30