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	$122.40	9.621%	$134.1761	$134.18	$134.20	$134.20
Purchase #2	$171.80	11.691%	$191.8851	$191.89	$191.90	$191.90
Purchase #3	$71.57	9.864%	$78.6297	$78.63	$78.65	$78.60
Purchase #4	$127.56	8.397%	$138.2712	$138.27	$138.25	$138.30
Purchase #5	$206.95	11.859%	$231.4922	$231.49	$231.50	$231.50
Purchase #6	$97.46	12.304%	$109.4515	$109.45	$109.45	$109.50
Purchase #7	$223.42	10.874%	$247.7147	$247.71	$247.70	$247.70
7 purchase totals =	$1,021.16		$1,131.6205	$1,131.62	$1,131.65	$1,131.70