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	$200.52	7.609%	$215.7776	$215.78	$215.80	$215.80
Purchase #2	$233.38	8.807%	$253.9338	$253.93	$253.95	$253.90
Purchase #3	$75.59	10.116%	$83.2367	$83.24	$83.25	$83.20
Purchase #4	$180.74	6.682%	$192.817	$192.82	$192.80	$192.80
Purchase #5	$119.25	7.112%	$127.7311	$127.73	$127.75	$127.70
Purchase #6	$25.78	5.365%	$27.1631	$27.16	$27.15	$27.20
Purchase #7	$151.78	9.472%	$166.1566	$166.16	$166.15	$166.20
7 purchase totals =	$987.04		$1,066.8159	$1,066.82	$1,066.85	$1,066.80