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	$31.27	3.541%	$32.3773	$32.38	$32.40	$32.40
Purchase #2	$37.83	9.571%	$41.4507	$41.45	$41.45	$41.50
Purchase #3	$14.37	3.244%	$14.8362	$14.84	$14.85	$14.80
Purchase #4	$169.93	11.537%	$189.5348	$189.53	$189.55	$189.50
Purchase #5	$9.25	13.673%	$10.5148	$10.51	$10.50	$10.50
Purchase #6	$165.31	6.393%	$175.8783	$175.88	$175.90	$175.90
Purchase #7	$152.82	8.663%	$166.0588	$166.06	$166.05	$166.10
7 purchase totals =	$580.78		$630.6509	$630.65	$630.70	$630.70