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	$68.48	4.824%	$71.7835	$71.78	$71.80	$71.80
Purchase #2	$206.25	7.356%	$221.4218	$221.42	$221.40	$221.40
Purchase #3	$217.83	13.716%	$247.7076	$247.71	$247.70	$247.70
Purchase #4	$231.88	10.163%	$255.446	$255.45	$255.45	$255.40
Purchase #5	$38.48	11.764%	$43.0068	$43.01	$43.00	$43.00
Purchase #6	$12.44	10.269%	$13.7175	$13.72	$13.70	$13.70
Purchase #7	$76.30	4.787%	$79.9525	$79.95	$79.95	$80.00
7 purchase totals =	$851.66		$933.0357	$933.04	$933.00	$933.00