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	$215.66	7.789%	$232.4578	$232.46	$232.45	$232.50
Purchase #2	$109.72	8.813%	$119.3896	$119.39	$119.40	$119.40
Purchase #3	$210.33	7.357%	$225.804	$225.80	$225.80	$225.80
Purchase #4	$55.55	3.249%	$57.3548	$57.35	$57.35	$57.40
Purchase #5	$74.27	11.169%	$82.5652	$82.57	$82.55	$82.60
Purchase #6	$39.90	13.185%	$45.1608	$45.16	$45.15	$45.20
Purchase #7	$249.64	9.533%	$273.4382	$273.44	$273.45	$273.40
7 purchase totals =	$955.07		$1,036.1704	$1,036.17	$1,036.15	$1,036.30