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	$42.83	5.157%	$45.0387	$45.04	$45.05	$45.00
Purchase #2	$75.96	8.658%	$82.5366	$82.54	$82.55	$82.50
Purchase #3	$5.32	7.622%	$5.7255	$5.73	$5.75	$5.70
Purchase #4	$98.89	12.767%	$111.5153	$111.52	$111.50	$111.50
Purchase #5	$235.42	5.526%	$248.4293	$248.43	$248.45	$248.40
Purchase #6	$67.76	10.521%	$74.889	$74.89	$74.90	$74.90
Purchase #7	$194.41	10.754%	$215.3169	$215.32	$215.30	$215.30
7 purchase totals =	$720.59		$783.4513	$783.47	$783.50	$783.30