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	$196.34	10.364%	$216.6887	$216.69	$216.70	$216.70
Purchase #2	$161.59	6.450%	$172.0126	$172.01	$172.00	$172.00
Purchase #3	$60.39	5.210%	$63.5363	$63.54	$63.55	$63.50
Purchase #4	$206.68	4.263%	$215.4908	$215.49	$215.50	$215.50
Purchase #5	$125.90	4.463%	$131.5189	$131.52	$131.50	$131.50
Purchase #6	$129.45	9.854%	$142.206	$142.21	$142.20	$142.20
Purchase #7	$35.99	3.758%	$37.3425	$37.34	$37.35	$37.30
7 purchase totals =	$916.34		$978.7958	$978.80	$978.80	$978.70