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	$184.90	12.808%	$208.582	$208.58	$208.60	$208.60
Purchase #2	$179.55	3.362%	$185.5865	$185.59	$185.60	$185.60
Purchase #3	$82.38	13.684%	$93.6529	$93.65	$93.65	$93.70
Purchase #4	$195.95	13.420%	$222.2465	$222.25	$222.25	$222.20
Purchase #5	$82.91	3.379%	$85.7115	$85.71	$85.70	$85.70
Purchase #6	$74.65	5.614%	$78.8409	$78.84	$78.85	$78.80
Purchase #7	$170.26	8.496%	$184.7253	$184.73	$184.75	$184.70
7 purchase totals =	$970.60		$1,059.3456	$1,059.35	$1,059.40	$1,059.30