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	$210.28	11.228%	$233.8902	$233.89	$233.90	$233.90
Purchase #2	$249.31	5.523%	$263.0794	$263.08	$263.10	$263.10
Purchase #3	$167.64	13.510%	$190.2882	$190.29	$190.30	$190.30
Purchase #4	$229.34	5.356%	$241.6235	$241.62	$241.60	$241.60
Purchase #5	$150.93	10.639%	$166.9874	$166.99	$167.00	$167.00
Purchase #6	$49.47	5.778%	$52.3284	$52.33	$52.35	$52.30
Purchase #7	$189.86	11.259%	$211.2363	$211.24	$211.25	$211.20
7 purchase totals =	$1,246.83		$1,359.4334	$1,359.44	$1,359.50	$1,359.40