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	$196.50	6.133%	$208.5513	$208.55	$208.55	$208.60
Purchase #2	$167.37	7.130%	$179.3035	$179.30	$179.30	$179.30
Purchase #3	$238.33	7.211%	$255.516	$255.52	$255.50	$255.50
Purchase #4	$170.52	5.214%	$179.4109	$179.41	$179.40	$179.40
Purchase #5	$72.69	11.216%	$80.8429	$80.84	$80.85	$80.80
Purchase #6	$29.27	10.455%	$32.3302	$32.33	$32.35	$32.30
Purchase #7	$222.99	8.540%	$242.0333	$242.03	$242.05	$242.00
7 purchase totals =	$1,097.67		$1,177.9881	$1,177.98	$1,178.00	$1,177.90