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	$222.94	11.567%	$248.7275	$248.73	$248.75	$248.70
Purchase #2	$106.73	10.317%	$117.7413	$117.74	$117.75	$117.70
Purchase #3	$176.48	12.278%	$198.1482	$198.15	$198.15	$198.10
Purchase #4	$199.97	9.183%	$218.3332	$218.33	$218.35	$218.30
Purchase #5	$164.90	5.446%	$173.8805	$173.88	$173.90	$173.90
Purchase #6	$84.74	6.696%	$90.4142	$90.41	$90.40	$90.40
Purchase #7	$119.34	10.488%	$131.8564	$131.86	$131.85	$131.90
7 purchase totals =	$1,075.10		$1,179.1013	$1,179.10	$1,179.15	$1,179.00