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	$209.27	7.599%	$225.1724	$225.17	$225.15	$225.20
Purchase #2	$114.59	12.250%	$128.6273	$128.63	$128.65	$128.60
Purchase #3	$66.46	8.701%	$72.2427	$72.24	$72.25	$72.20
Purchase #4	$152.34	6.714%	$162.5681	$162.57	$162.55	$162.60
Purchase #5	$152.67	12.766%	$172.1599	$172.16	$172.15	$172.20
Purchase #6	$210.88	7.747%	$227.2169	$227.22	$227.20	$227.20
Purchase #7	$193.66	11.462%	$215.8573	$215.86	$215.85	$215.90
7 purchase totals =	$1,099.87		$1,203.8446	$1,203.85	$1,203.80	$1,203.90