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	$168.51	12.121%	$188.9351	$188.94	$188.95	$188.90
Purchase #2	$102.61	13.861%	$116.8328	$116.83	$116.85	$116.80
Purchase #3	$202.43	12.270%	$227.2682	$227.27	$227.25	$227.30
Purchase #4	$68.58	6.159%	$72.8038	$72.80	$72.80	$72.80
Purchase #5	$211.72	8.204%	$229.0895	$229.09	$229.10	$229.10
Purchase #6	$182.57	13.314%	$206.8774	$206.88	$206.90	$206.90
Purchase #7	$139.30	10.208%	$153.5197	$153.52	$153.50	$153.50
7 purchase totals =	$1,075.72		$1,195.3265	$1,195.33	$1,195.35	$1,195.30