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	$209.81	13.621%	$238.3882	$238.39	$238.40	$238.40
Purchase #2	$72.37	8.365%	$78.4238	$78.42	$78.40	$78.40
Purchase #3	$202.63	6.739%	$216.2852	$216.29	$216.30	$216.30
Purchase #4	$236.88	10.414%	$261.5487	$261.55	$261.55	$261.50
Purchase #5	$43.85	5.255%	$46.1543	$46.15	$46.15	$46.20
Purchase #6	$184.81	9.602%	$202.5555	$202.56	$202.55	$202.60
Purchase #7	$116.42	9.507%	$127.488	$127.49	$127.50	$127.50
7 purchase totals =	$1,066.77		$1,170.8437	$1,170.85	$1,170.85	$1,170.90