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	$141.95	7.274%	$152.2754	$152.28	$152.30	$152.30
Purchase #2	$105.27	3.157%	$108.5934	$108.59	$108.60	$108.60
Purchase #3	$244.34	12.355%	$274.5282	$274.53	$274.55	$274.50
Purchase #4	$16.75	7.677%	$18.0359	$18.04	$18.05	$18.00
Purchase #5	$118.72	10.699%	$131.4219	$131.42	$131.40	$131.40
Purchase #6	$172.58	8.512%	$187.27	$187.27	$187.25	$187.30
Purchase #7	$46.25	10.691%	$51.1946	$51.19	$51.20	$51.20
7 purchase totals =	$845.86		$923.3194	$923.32	$923.35	$923.30