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	$131.45	3.873%	$136.5411	$136.54	$136.55	$136.50
Purchase #2	$156.73	11.337%	$174.4985	$174.50	$174.50	$174.50
Purchase #3	$56.53	5.580%	$59.6844	$59.68	$59.70	$59.70
Purchase #4	$164.78	6.717%	$175.8483	$175.85	$175.85	$175.80
Purchase #5	$154.91	13.843%	$176.3542	$176.35	$176.35	$176.40
Purchase #6	$66.33	9.503%	$72.6333	$72.63	$72.65	$72.60
Purchase #7	$238.65	11.533%	$266.1735	$266.17	$266.15	$266.20
7 purchase totals =	$969.38		$1,061.7333	$1,061.72	$1,061.75	$1,061.70