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	$153.83	8.574%	$167.0194	$167.02	$167.00	$167.00
Purchase #2	$6.51	12.364%	$7.3149	$7.31	$7.30	$7.30
Purchase #3	$186.26	10.503%	$205.8229	$205.82	$205.80	$205.80
Purchase #4	$219.81	9.595%	$240.9008	$240.90	$240.90	$240.90
Purchase #5	$233.95	9.457%	$256.0747	$256.07	$256.05	$256.10
Purchase #6	$6.89	10.435%	$7.609	$7.61	$7.60	$7.60
Purchase #7	$50.77	4.867%	$53.241	$53.24	$53.25	$53.20
7 purchase totals =	$858.02		$937.9827	$937.97	$937.90	$937.90