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	$38.68	6.405%	$41.1575	$41.16	$41.15	$41.20
Purchase #2	$41.41	10.149%	$45.6127	$45.61	$45.60	$45.60
Purchase #3	$25.43	6.338%	$27.0418	$27.04	$27.05	$27.00
Purchase #4	$143.89	11.408%	$160.305	$160.31	$160.30	$160.30
Purchase #5	$33.72	10.836%	$37.3739	$37.37	$37.35	$37.40
Purchase #6	$197.64	11.775%	$220.9121	$220.91	$220.90	$220.90
Purchase #7	$148.64	9.112%	$162.1841	$162.18	$162.20	$162.20
7 purchase totals =	$629.41		$694.5871	$694.58	$694.55	$694.60