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	$61.25	11.696%	$68.4138	$68.41	$68.40	$68.40
Purchase #2	$200.34	4.772%	$209.9002	$209.90	$209.90	$209.90
Purchase #3	$163.80	11.347%	$182.3864	$182.39	$182.40	$182.40
Purchase #4	$108.87	11.797%	$121.7134	$121.71	$121.70	$121.70
Purchase #5	$120.31	5.565%	$127.0053	$127.01	$127.00	$127.00
Purchase #6	$87.98	3.147%	$90.7487	$90.75	$90.75	$90.70
Purchase #7	$201.90	7.400%	$216.8406	$216.84	$216.85	$216.80
7 purchase totals =	$944.45		$1,017.0084	$1,017.01	$1,017.00	$1,016.90