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	$50.76	5.816%	$53.7122	$53.71	$53.70	$53.70
Purchase #2	$105.36	13.302%	$119.375	$119.38	$119.40	$119.40
Purchase #3	$40.30	7.825%	$43.4535	$43.45	$43.45	$43.50
Purchase #4	$231.81	13.377%	$262.8192	$262.82	$262.80	$262.80
Purchase #5	$149.75	8.455%	$162.4114	$162.41	$162.40	$162.40
Purchase #6	$135.27	7.709%	$145.698	$145.70	$145.70	$145.70
Purchase #7	$207.77	7.530%	$223.4151	$223.42	$223.40	$223.40
7 purchase totals =	$921.02		$1,010.8844	$1,010.89	$1,010.85	$1,010.90