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	$54.72	13.110%	$61.8938	$61.89	$61.90	$61.90
Purchase #2	$152.33	10.769%	$168.7344	$168.73	$168.75	$168.70
Purchase #3	$229.32	13.538%	$260.3653	$260.37	$260.35	$260.40
Purchase #4	$75.31	9.467%	$82.4396	$82.44	$82.45	$82.40
Purchase #5	$227.77	5.151%	$239.5024	$239.50	$239.50	$239.50
Purchase #6	$79.34	4.379%	$82.8143	$82.81	$82.80	$82.80
Purchase #7	$212.71	3.585%	$220.3357	$220.34	$220.35	$220.30
7 purchase totals =	$1,031.50		$1,116.0855	$1,116.08	$1,116.10	$1,116.00