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	$105.55	7.553%	$113.5222	$113.52	$113.50	$113.50
Purchase #2	$204.47	5.158%	$215.0166	$215.02	$215.00	$215.00
Purchase #3	$250.94	8.614%	$272.556	$272.56	$272.55	$272.60
Purchase #4	$8.39	7.749%	$9.0401	$9.04	$9.05	$9.00
Purchase #5	$179.76	10.248%	$198.1818	$198.18	$198.20	$198.20
Purchase #6	$228.41	11.853%	$255.4834	$255.48	$255.50	$255.50
Purchase #7	$71.78	9.736%	$78.7685	$78.77	$78.75	$78.80
7 purchase totals =	$1,049.30		$1,142.5686	$1,142.57	$1,142.55	$1,142.60