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	$210.96	11.656%	$235.5495	$235.55	$235.55	$235.50
Purchase #2	$59.36	5.404%	$62.5678	$62.57	$62.55	$62.60
Purchase #3	$157.83	10.769%	$174.8267	$174.83	$174.85	$174.80
Purchase #4	$95.59	7.188%	$102.461	$102.46	$102.45	$102.50
Purchase #5	$29.69	3.874%	$30.8402	$30.84	$30.85	$30.80
Purchase #6	$64.66	12.612%	$72.8149	$72.81	$72.80	$72.80
Purchase #7	$51.42	9.228%	$56.165	$56.17	$56.15	$56.20
7 purchase totals =	$669.51		$735.2251	$735.23	$735.20	$735.20