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	$113.49	5.230%	$119.4255	$119.43	$119.45	$119.40
Purchase #2	$169.65	6.437%	$180.5704	$180.57	$180.55	$180.60
Purchase #3	$154.29	10.131%	$169.9211	$169.92	$169.90	$169.90
Purchase #4	$230.32	5.520%	$243.0337	$243.03	$243.05	$243.00
Purchase #5	$94.69	7.594%	$101.8808	$101.88	$101.90	$101.90
Purchase #6	$135.93	4.383%	$141.8878	$141.89	$141.90	$141.90
Purchase #7	$140.98	9.443%	$154.2927	$154.29	$154.30	$154.30
7 purchase totals =	$1,039.35		$1,111.0120	$1,111.01	$1,111.05	$1,111.00