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	$136.48	3.344%	$141.0439	$141.04	$141.05	$141.00
Purchase #2	$204.37	11.119%	$227.0939	$227.09	$227.10	$227.10
Purchase #3	$177.35	6.504%	$188.8848	$188.88	$188.90	$188.90
Purchase #4	$98.31	5.531%	$103.7475	$103.75	$103.75	$103.70
Purchase #5	$166.89	8.132%	$180.4615	$180.46	$180.45	$180.50
Purchase #6	$140.29	3.162%	$144.726	$144.73	$144.75	$144.70
Purchase #7	$80.83	6.248%	$85.8803	$85.88	$85.90	$85.90
7 purchase totals =	$1,004.52		$1,071.8379	$1,071.83	$1,071.90	$1,071.80