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	$77.95	9.669%	$85.487	$85.49	$85.50	$85.50
Purchase #2	$167.84	8.572%	$182.2272	$182.23	$182.25	$182.20
Purchase #3	$148.81	11.217%	$165.502	$165.50	$165.50	$165.50
Purchase #4	$101.72	7.653%	$109.5046	$109.50	$109.50	$109.50
Purchase #5	$150.63	7.518%	$161.9544	$161.95	$161.95	$162.00
Purchase #6	$158.85	10.461%	$175.4673	$175.47	$175.45	$175.50
Purchase #7	$247.31	10.779%	$273.9675	$273.97	$273.95	$274.00
7 purchase totals =	$1,053.11		$1,154.1100	$1,154.11	$1,154.10	$1,154.20