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	$141.66	9.306%	$154.8429	$154.84	$154.85	$154.80
Purchase #2	$243.79	4.744%	$255.3554	$255.36	$255.35	$255.40
Purchase #3	$54.85	6.359%	$58.3379	$58.34	$58.35	$58.30
Purchase #4	$92.72	4.493%	$96.8859	$96.89	$96.90	$96.90
Purchase #5	$14.66	5.382%	$15.449	$15.45	$15.45	$15.40
Purchase #6	$168.25	8.393%	$182.3712	$182.37	$182.35	$182.40
Purchase #7	$136.51	11.573%	$152.3083	$152.31	$152.30	$152.30
7 purchase totals =	$852.44		$915.5506	$915.56	$915.55	$915.50