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	$147.31	13.342%	$166.9641	$166.96	$166.95	$167.00
Purchase #2	$7.73	8.518%	$8.3884	$8.39	$8.40	$8.40
Purchase #3	$240.48	10.184%	$264.9705	$264.97	$264.95	$265.00
Purchase #4	$77.47	10.849%	$85.8747	$85.87	$85.85	$85.90
Purchase #5	$89.43	11.206%	$99.4515	$99.45	$99.45	$99.50
Purchase #6	$153.64	5.826%	$162.5911	$162.59	$162.60	$162.60
Purchase #7	$240.47	3.789%	$249.5814	$249.58	$249.60	$249.60
7 purchase totals =	$956.53		$1,037.8217	$1,037.81	$1,037.80	$1,038.00