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	$84.82	12.570%	$95.4819	$95.48	$95.50	$95.50
Purchase #2	$215.76	9.452%	$236.1536	$236.15	$236.15	$236.20
Purchase #3	$167.37	9.137%	$182.6626	$182.66	$182.65	$182.70
Purchase #4	$116.71	10.292%	$128.7218	$128.72	$128.70	$128.70
Purchase #5	$245.47	8.314%	$265.8784	$265.88	$265.90	$265.90
Purchase #6	$56.34	6.392%	$59.9413	$59.94	$59.95	$59.90
Purchase #7	$154.68	11.558%	$172.5579	$172.56	$172.55	$172.60
7 purchase totals =	$1,041.15		$1,141.3975	$1,141.39	$1,141.40	$1,141.50