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	$110.76	12.731%	$124.8609	$124.86	$124.85	$124.90
Purchase #2	$163.67	11.521%	$182.5264	$182.53	$182.55	$182.50
Purchase #3	$103.64	8.385%	$112.3302	$112.33	$112.35	$112.30
Purchase #4	$136.72	6.575%	$145.7093	$145.71	$145.70	$145.70
Purchase #5	$68.93	12.735%	$77.7082	$77.71	$77.70	$77.70
Purchase #6	$223.65	3.335%	$231.1087	$231.11	$231.10	$231.10
Purchase #7	$212.98	4.480%	$222.5215	$222.52	$222.50	$222.50
7 purchase totals =	$1,020.35		$1,096.7652	$1,096.77	$1,096.75	$1,096.70