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	$53.58	11.726%	$59.8628	$59.86	$59.85	$59.90
Purchase #2	$138.44	10.337%	$152.7505	$152.75	$152.75	$152.80
Purchase #3	$241.57	3.720%	$250.5564	$250.56	$250.55	$250.60
Purchase #4	$67.65	4.188%	$70.4832	$70.48	$70.50	$70.50
Purchase #5	$112.74	13.414%	$127.8629	$127.86	$127.85	$127.90
Purchase #6	$76.26	6.131%	$80.9355	$80.94	$80.95	$80.90
Purchase #7	$224.76	13.265%	$254.5744	$254.57	$254.55	$254.60
7 purchase totals =	$915.00		$997.0257	$997.02	$997.00	$997.20