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	$156.51	11.481%	$174.4789	$174.48	$174.50	$174.50
Purchase #2	$87.59	5.485%	$92.3943	$92.39	$92.40	$92.40
Purchase #3	$90.33	10.320%	$99.6521	$99.65	$99.65	$99.70
Purchase #4	$72.79	13.118%	$82.3386	$82.34	$82.35	$82.30
Purchase #5	$178.76	8.776%	$194.448	$194.45	$194.45	$194.40
Purchase #6	$113.33	11.155%	$125.972	$125.97	$125.95	$126.00
Purchase #7	$135.31	3.146%	$139.5669	$139.57	$139.55	$139.60
7 purchase totals =	$834.62		$908.8508	$908.85	$908.85	$908.90