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	$62.75	7.314%	$67.3395	$67.34	$67.35	$67.30
Purchase #2	$39.85	5.541%	$42.0581	$42.06	$42.05	$42.10
Purchase #3	$196.65	10.617%	$217.5283	$217.53	$217.55	$217.50
Purchase #4	$37.72	9.854%	$41.4369	$41.44	$41.45	$41.40
Purchase #5	$85.76	7.171%	$91.9098	$91.91	$91.90	$91.90
Purchase #6	$34.36	8.600%	$37.315	$37.32	$37.30	$37.30
Purchase #7	$178.95	6.157%	$189.968	$189.97	$189.95	$190.00
7 purchase totals =	$636.04		$687.5556	$687.57	$687.55	$687.50