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	$82.53	4.552%	$86.2868	$86.29	$86.30	$86.30
Purchase #2	$71.73	9.134%	$78.2818	$78.28	$78.30	$78.30
Purchase #3	$82.83	5.151%	$87.0966	$87.10	$87.10	$87.10
Purchase #4	$119.96	11.662%	$133.9497	$133.95	$133.95	$133.90
Purchase #5	$182.84	4.233%	$190.5796	$190.58	$190.60	$190.60
Purchase #6	$136.96	9.799%	$150.3807	$150.38	$150.40	$150.40
Purchase #7	$11.92	10.653%	$13.1898	$13.19	$13.20	$13.20
7 purchase totals =	$688.77		$739.7650	$739.77	$739.85	$739.80