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	$216.56	13.223%	$245.1957	$245.20	$245.20	$245.20
Purchase #2	$91.59	11.388%	$102.0203	$102.02	$102.00	$102.00
Purchase #3	$161.28	13.333%	$182.7835	$182.78	$182.80	$182.80
Purchase #4	$29.93	7.262%	$32.1035	$32.10	$32.10	$32.10
Purchase #5	$111.94	11.293%	$124.5814	$124.58	$124.60	$124.60
Purchase #6	$78.65	12.304%	$88.3271	$88.33	$88.35	$88.30
Purchase #7	$242.84	5.224%	$255.526	$255.53	$255.55	$255.50
7 purchase totals =	$932.79		$1,030.5375	$1,030.54	$1,030.60	$1,030.50