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	$64.30	4.821%	$67.3999	$67.40	$67.40	$67.40
Purchase #2	$121.74	6.204%	$129.2927	$129.29	$129.30	$129.30
Purchase #3	$144.46	5.365%	$152.2103	$152.21	$152.20	$152.20
Purchase #4	$30.59	3.305%	$31.601	$31.60	$31.60	$31.60
Purchase #5	$47.39	6.647%	$50.54	$50.54	$50.55	$50.50
Purchase #6	$173.37	13.698%	$197.1182	$197.12	$197.10	$197.10
Purchase #7	$34.70	12.708%	$39.1097	$39.11	$39.10	$39.10
7 purchase totals =	$616.55		$667.2718	$667.27	$667.25	$667.20