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	$70.96	10.582%	$78.469	$78.47	$78.45	$78.50
Purchase #2	$132.48	3.282%	$136.828	$136.83	$136.85	$136.80
Purchase #3	$215.85	6.424%	$229.7162	$229.72	$229.70	$229.70
Purchase #4	$81.71	11.115%	$90.7921	$90.79	$90.80	$90.80
Purchase #5	$125.69	12.631%	$141.5659	$141.57	$141.55	$141.60
Purchase #6	$194.48	8.805%	$211.604	$211.60	$211.60	$211.60
Purchase #7	$193.52	5.509%	$204.181	$204.18	$204.20	$204.20
7 purchase totals =	$1,014.69		$1,093.1562	$1,093.16	$1,093.15	$1,093.20