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	$64.33	8.455%	$69.7691	$69.77	$69.75	$69.80
Purchase #2	$71.58	4.620%	$74.887	$74.89	$74.90	$74.90
Purchase #3	$172.69	13.865%	$196.6335	$196.63	$196.65	$196.60
Purchase #4	$38.55	11.332%	$42.9185	$42.92	$42.90	$42.90
Purchase #5	$69.91	10.821%	$77.475	$77.48	$77.50	$77.50
Purchase #6	$82.82	11.679%	$92.4925	$92.49	$92.50	$92.50
Purchase #7	$137.65	12.612%	$155.0104	$155.01	$155.00	$155.00
7 purchase totals =	$637.53		$709.1860	$709.19	$709.20	$709.20