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	$134.77	7.606%	$145.0206	$145.02	$145.00	$145.00
Purchase #2	$105.79	3.702%	$109.7063	$109.71	$109.70	$109.70
Purchase #3	$78.58	11.536%	$87.645	$87.65	$87.65	$87.60
Purchase #4	$53.90	10.683%	$59.6581	$59.66	$59.65	$59.70
Purchase #5	$38.88	3.813%	$40.3625	$40.36	$40.35	$40.40
Purchase #6	$28.79	13.232%	$32.5995	$32.60	$32.60	$32.60
Purchase #7	$105.88	4.671%	$110.8257	$110.83	$110.85	$110.80
7 purchase totals =	$546.59		$585.8177	$585.83	$585.80	$585.80