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	$72.97	7.397%	$78.3676	$78.37	$78.35	$78.40
Purchase #2	$240.34	3.580%	$248.9442	$248.94	$248.95	$248.90
Purchase #3	$222.87	8.634%	$242.1126	$242.11	$242.10	$242.10
Purchase #4	$214.60	10.486%	$237.103	$237.10	$237.10	$237.10
Purchase #5	$123.90	6.154%	$131.5248	$131.52	$131.50	$131.50
Purchase #6	$175.48	5.747%	$185.5648	$185.56	$185.55	$185.60
Purchase #7	$124.52	7.526%	$133.8914	$133.89	$133.90	$133.90
7 purchase totals =	$1,174.68		$1,257.5084	$1,257.49	$1,257.45	$1,257.50