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	$147.67	13.378%	$167.4253	$167.43	$167.45	$167.40
Purchase #2	$82.90	11.481%	$92.4177	$92.42	$92.40	$92.40
Purchase #3	$218.34	3.244%	$225.4229	$225.42	$225.40	$225.40
Purchase #4	$10.68	11.820%	$11.9424	$11.94	$11.95	$11.90
Purchase #5	$104.56	12.646%	$117.7827	$117.78	$117.80	$117.80
Purchase #6	$154.67	10.730%	$171.2661	$171.27	$171.25	$171.30
Purchase #7	$216.48	3.423%	$223.8901	$223.89	$223.90	$223.90
7 purchase totals =	$935.30		$1,010.1472	$1,010.15	$1,010.15	$1,010.10