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	$233.65	9.334%	$255.4589	$255.46	$255.45	$255.50
Purchase #2	$66.75	10.638%	$73.8509	$73.85	$73.85	$73.90
Purchase #3	$38.74	13.700%	$44.0474	$44.05	$44.05	$44.00
Purchase #4	$100.75	10.744%	$111.5746	$111.57	$111.55	$111.60
Purchase #5	$102.75	11.684%	$114.7553	$114.76	$114.75	$114.80
Purchase #6	$13.78	13.294%	$15.6119	$15.61	$15.60	$15.60
Purchase #7	$186.79	11.370%	$208.028	$208.03	$208.05	$208.00
7 purchase totals =	$743.21		$823.3270	$823.33	$823.30	$823.40