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	$19.90	10.276%	$21.9449	$21.94	$21.95	$21.90
Purchase #2	$130.82	13.691%	$148.7306	$148.73	$148.75	$148.70
Purchase #3	$72.53	7.582%	$78.0292	$78.03	$78.05	$78.00
Purchase #4	$201.38	11.774%	$225.0905	$225.09	$225.10	$225.10
Purchase #5	$211.33	5.641%	$223.2511	$223.25	$223.25	$223.30
Purchase #6	$172.83	11.221%	$192.2233	$192.22	$192.20	$192.20
Purchase #7	$141.90	3.528%	$146.9062	$146.91	$146.90	$146.90
7 purchase totals =	$950.69		$1,036.1758	$1,036.17	$1,036.20	$1,036.10