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	$160.83	11.380%	$179.1325	$179.13	$179.15	$179.10
Purchase #2	$147.71	6.173%	$156.8281	$156.83	$156.85	$156.80
Purchase #3	$127.38	11.417%	$141.923	$141.92	$141.90	$141.90
Purchase #4	$129.76	13.706%	$147.5449	$147.54	$147.55	$147.50
Purchase #5	$156.81	3.691%	$162.5979	$162.60	$162.60	$162.60
Purchase #6	$225.37	10.742%	$249.5792	$249.58	$249.60	$249.60
Purchase #7	$108.67	10.730%	$120.3303	$120.33	$120.35	$120.30
7 purchase totals =	$1,056.53		$1,157.9359	$1,157.93	$1,158.00	$1,157.80