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	$204.67	9.392%	$223.8926	$223.89	$223.90	$223.90
Purchase #2	$113.59	5.477%	$119.8113	$119.81	$119.80	$119.80
Purchase #3	$118.46	8.860%	$128.9556	$128.96	$128.95	$129.00
Purchase #4	$49.39	10.799%	$54.7236	$54.72	$54.70	$54.70
Purchase #5	$172.50	10.303%	$190.2727	$190.27	$190.25	$190.30
Purchase #6	$194.92	4.646%	$203.976	$203.98	$204.00	$204.00
Purchase #7	$141.41	10.273%	$155.937	$155.94	$155.95	$155.90
7 purchase totals =	$994.94		$1,077.5688	$1,077.57	$1,077.55	$1,077.60