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	$220.91	5.796%	$233.7139	$233.71	$233.70	$233.70
Purchase #2	$243.97	8.634%	$265.0344	$265.03	$265.05	$265.00
Purchase #3	$38.55	6.352%	$40.9987	$41.00	$41.00	$41.00
Purchase #4	$73.77	8.551%	$80.0781	$80.08	$80.10	$80.10
Purchase #5	$111.57	10.690%	$123.4968	$123.50	$123.50	$123.50
Purchase #6	$157.69	10.655%	$174.4919	$174.49	$174.50	$174.50
Purchase #7	$75.28	4.329%	$78.5389	$78.54	$78.55	$78.50
7 purchase totals =	$921.74		$996.3527	$996.35	$996.40	$996.30