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	$188.95	12.520%	$212.6065	$212.61	$212.60	$212.60
Purchase #2	$168.82	4.455%	$176.3409	$176.34	$176.35	$176.30
Purchase #3	$115.48	6.790%	$123.3211	$123.32	$123.30	$123.30
Purchase #4	$229.94	6.200%	$244.1963	$244.20	$244.20	$244.20
Purchase #5	$91.56	13.114%	$103.5672	$103.57	$103.55	$103.60
Purchase #6	$19.27	11.599%	$21.5051	$21.51	$21.50	$21.50
Purchase #7	$196.95	10.692%	$218.0079	$218.01	$218.00	$218.00
7 purchase totals =	$1,010.97		$1,099.5450	$1,099.56	$1,099.50	$1,099.50