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	$93.59	9.260%	$102.2564	$102.26	$102.25	$102.30
Purchase #2	$156.31	4.858%	$163.9035	$163.90	$163.90	$163.90
Purchase #3	$25.89	11.173%	$28.7827	$28.78	$28.80	$28.80
Purchase #4	$13.69	10.777%	$15.1654	$15.17	$15.15	$15.20
Purchase #5	$90.25	13.674%	$102.5908	$102.59	$102.60	$102.60
Purchase #6	$178.78	10.103%	$196.8421	$196.84	$196.85	$196.80
Purchase #7	$96.27	9.758%	$105.664	$105.66	$105.65	$105.70
7 purchase totals =	$654.78		$715.2049	$715.20	$715.20	$715.30