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	$222.90	5.478%	$235.1105	$235.11	$235.10	$235.10
Purchase #2	$77.80	10.794%	$86.1977	$86.20	$86.20	$86.20
Purchase #3	$209.93	13.821%	$238.9444	$238.94	$238.95	$238.90
Purchase #4	$150.35	9.863%	$165.179	$165.18	$165.20	$165.20
Purchase #5	$196.48	13.456%	$222.9183	$222.92	$222.90	$222.90
Purchase #6	$84.78	11.578%	$94.5958	$94.60	$94.60	$94.60
Purchase #7	$130.89	11.574%	$146.0392	$146.04	$146.05	$146.00
7 purchase totals =	$1,073.13		$1,188.9849	$1,188.99	$1,189.00	$1,188.90