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	$141.54	4.691%	$148.1796	$148.18	$148.20	$148.20
Purchase #2	$215.85	8.423%	$234.031	$234.03	$234.05	$234.00
Purchase #3	$211.25	5.359%	$222.5709	$222.57	$222.55	$222.60
Purchase #4	$211.63	13.809%	$240.854	$240.85	$240.85	$240.90
Purchase #5	$29.90	6.380%	$31.8076	$31.81	$31.80	$31.80
Purchase #6	$196.56	10.861%	$217.9084	$217.91	$217.90	$217.90
Purchase #7	$152.88	12.859%	$172.5388	$172.54	$172.55	$172.50
7 purchase totals =	$1,159.61		$1,267.8903	$1,267.89	$1,267.90	$1,267.90