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	$55.89	6.871%	$59.7302	$59.73	$59.75	$59.70
Purchase #2	$5.67	12.533%	$6.3806	$6.38	$6.40	$6.40
Purchase #3	$250.60	6.138%	$265.9818	$265.98	$266.00	$266.00
Purchase #4	$16.51	11.220%	$18.3624	$18.36	$18.35	$18.40
Purchase #5	$191.61	13.771%	$217.9966	$218.00	$218.00	$218.00
Purchase #6	$71.45	9.556%	$78.2778	$78.28	$78.30	$78.30
Purchase #7	$170.46	5.395%	$179.6563	$179.66	$179.65	$179.70
7 purchase totals =	$762.19		$826.3857	$826.39	$826.45	$826.50