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	$68.31	6.254%	$72.5821	$72.58	$72.60	$72.60
Purchase #2	$179.54	11.725%	$200.5911	$200.59	$200.60	$200.60
Purchase #3	$202.48	6.262%	$215.1593	$215.16	$215.15	$215.20
Purchase #4	$236.44	11.806%	$264.3541	$264.35	$264.35	$264.40
Purchase #5	$25.56	10.744%	$28.3062	$28.31	$28.30	$28.30
Purchase #6	$226.80	5.336%	$238.902	$238.90	$238.90	$238.90
Purchase #7	$34.25	5.733%	$36.2136	$36.21	$36.20	$36.20
7 purchase totals =	$973.38		$1,056.1084	$1,056.10	$1,056.10	$1,056.20