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	$205.82	9.376%	$225.1177	$225.12	$225.10	$225.10
Purchase #2	$64.31	10.693%	$71.1867	$71.19	$71.20	$71.20
Purchase #3	$134.83	12.874%	$152.188	$152.19	$152.20	$152.20
Purchase #4	$192.70	13.719%	$219.1365	$219.14	$219.15	$219.10
Purchase #5	$33.25	6.693%	$35.4754	$35.48	$35.50	$35.50
Purchase #6	$205.37	5.499%	$216.6633	$216.66	$216.65	$216.70
Purchase #7	$78.59	13.863%	$89.4849	$89.48	$89.50	$89.50
7 purchase totals =	$914.87		$1,009.2525	$1,009.26	$1,009.30	$1,009.30