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	$249.82	13.627%	$283.863	$283.86	$283.85	$283.90
Purchase #2	$232.86	4.645%	$243.6763	$243.68	$243.70	$243.70
Purchase #3	$116.91	6.205%	$124.1643	$124.16	$124.15	$124.20
Purchase #4	$87.79	7.464%	$94.3426	$94.34	$94.35	$94.30
Purchase #5	$161.29	11.166%	$179.2996	$179.30	$179.30	$179.30
Purchase #6	$94.61	4.205%	$98.5884	$98.59	$98.60	$98.60
Purchase #7	$64.64	11.689%	$72.1958	$72.20	$72.20	$72.20
7 purchase totals =	$1,007.92		$1,096.1300	$1,096.13	$1,096.15	$1,096.20