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	$63.87	11.660%	$71.3172	$71.32	$71.30	$71.30
Purchase #2	$202.32	4.580%	$211.5863	$211.59	$211.60	$211.60
Purchase #3	$185.31	6.472%	$197.3033	$197.30	$197.30	$197.30
Purchase #4	$104.85	6.321%	$111.4776	$111.48	$111.50	$111.50
Purchase #5	$206.33	9.336%	$225.593	$225.59	$225.60	$225.60
Purchase #6	$201.95	4.574%	$211.1872	$211.19	$211.20	$211.20
Purchase #7	$139.61	12.291%	$156.7695	$156.77	$156.75	$156.80
7 purchase totals =	$1,104.24		$1,185.2341	$1,185.24	$1,185.25	$1,185.30