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	$226.62	6.269%	$240.8268	$240.83	$240.85	$240.80
Purchase #2	$225.61	5.763%	$238.6119	$238.61	$238.60	$238.60
Purchase #3	$64.98	10.672%	$71.9147	$71.91	$71.90	$71.90
Purchase #4	$207.47	12.648%	$233.7108	$233.71	$233.70	$233.70
Purchase #5	$49.84	13.344%	$56.4906	$56.49	$56.50	$56.50
Purchase #6	$207.33	11.615%	$231.4114	$231.41	$231.40	$231.40
Purchase #7	$105.80	3.249%	$109.2374	$109.24	$109.25	$109.20
7 purchase totals =	$1,087.65		$1,182.2036	$1,182.20	$1,182.20	$1,182.10