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	$183.68	11.834%	$205.4167	$205.42	$205.40	$205.40
Purchase #2	$209.99	8.307%	$227.4339	$227.43	$227.45	$227.40
Purchase #3	$84.96	4.628%	$88.8919	$88.89	$88.90	$88.90
Purchase #4	$173.53	10.333%	$191.4609	$191.46	$191.45	$191.50
Purchase #5	$110.75	5.546%	$116.8922	$116.89	$116.90	$116.90
Purchase #6	$119.59	3.399%	$123.6549	$123.65	$123.65	$123.70
Purchase #7	$90.56	3.423%	$93.6599	$93.66	$93.65	$93.70
7 purchase totals =	$973.06		$1,047.4104	$1,047.40	$1,047.40	$1,047.50