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	$67.38	7.137%	$72.1889	$72.19	$72.20	$72.20
Purchase #2	$66.61	7.764%	$71.7816	$71.78	$71.80	$71.80
Purchase #3	$53.90	4.513%	$56.3325	$56.33	$56.35	$56.30
Purchase #4	$119.42	11.189%	$132.7819	$132.78	$132.80	$132.80
Purchase #5	$11.98	4.573%	$12.5278	$12.53	$12.55	$12.50
Purchase #6	$91.58	10.270%	$100.9853	$100.99	$101.00	$101.00
Purchase #7	$65.88	6.601%	$70.2287	$70.23	$70.25	$70.20
7 purchase totals =	$476.75		$516.8267	$516.83	$516.95	$516.80