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	$63.91	3.654%	$66.2453	$66.25	$66.25	$66.20
Purchase #2	$167.81	10.788%	$185.9133	$185.91	$185.90	$185.90
Purchase #3	$196.39	6.201%	$208.5681	$208.57	$208.55	$208.60
Purchase #4	$31.82	3.299%	$32.8697	$32.87	$32.85	$32.90
Purchase #5	$250.63	4.301%	$261.4096	$261.41	$261.40	$261.40
Purchase #6	$232.91	11.754%	$260.2862	$260.29	$260.30	$260.30
Purchase #7	$94.99	4.231%	$99.009	$99.01	$99.00	$99.00
7 purchase totals =	$1,038.46		$1,114.3012	$1,114.31	$1,114.25	$1,114.30