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	$55.90	11.828%	$62.5119	$62.51	$62.50	$62.50
Purchase #2	$171.33	12.814%	$193.2842	$193.28	$193.30	$193.30
Purchase #3	$80.47	13.429%	$91.2763	$91.28	$91.30	$91.30
Purchase #4	$226.55	11.621%	$252.8774	$252.88	$252.90	$252.90
Purchase #5	$88.76	5.455%	$93.6019	$93.60	$93.60	$93.60
Purchase #6	$101.41	3.396%	$104.8539	$104.85	$104.85	$104.90
Purchase #7	$219.48	13.191%	$248.4316	$248.43	$248.45	$248.40
7 purchase totals =	$943.90		$1,046.8372	$1,046.83	$1,046.90	$1,046.90