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	$67.36	13.567%	$76.4987	$76.50	$76.50	$76.50
Purchase #2	$162.60	12.465%	$182.8681	$182.87	$182.85	$182.90
Purchase #3	$84.71	6.738%	$90.4178	$90.42	$90.40	$90.40
Purchase #4	$204.69	13.455%	$232.231	$232.23	$232.25	$232.20
Purchase #5	$99.67	12.113%	$111.743	$111.74	$111.75	$111.70
Purchase #6	$137.33	4.854%	$143.996	$144.00	$144.00	$144.00
Purchase #7	$167.45	12.298%	$188.043	$188.04	$188.05	$188.00
7 purchase totals =	$923.81		$1,025.7976	$1,025.80	$1,025.80	$1,025.70