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	$91.39	11.734%	$102.1137	$102.11	$102.10	$102.10
Purchase #2	$42.43	3.214%	$43.7937	$43.79	$43.80	$43.80
Purchase #3	$123.77	13.425%	$140.3861	$140.39	$140.40	$140.40
Purchase #4	$228.31	6.466%	$243.0725	$243.07	$243.05	$243.10
Purchase #5	$227.29	6.250%	$241.4956	$241.50	$241.50	$241.50
Purchase #6	$96.60	7.173%	$103.5291	$103.53	$103.55	$103.50
Purchase #7	$196.56	6.201%	$208.7487	$208.75	$208.75	$208.70
7 purchase totals =	$1,006.35		$1,083.1394	$1,083.14	$1,083.15	$1,083.10