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	$219.32	8.662%	$238.3175	$238.32	$238.30	$238.30
Purchase #2	$225.82	6.677%	$240.898	$240.90	$240.90	$240.90
Purchase #3	$177.39	10.854%	$196.6439	$196.64	$196.65	$196.60
Purchase #4	$22.61	11.430%	$25.1943	$25.19	$25.20	$25.20
Purchase #5	$223.60	4.571%	$233.8208	$233.82	$233.80	$233.80
Purchase #6	$114.73	7.745%	$123.6158	$123.62	$123.60	$123.60
Purchase #7	$24.44	3.705%	$25.3455	$25.35	$25.35	$25.30
7 purchase totals =	$1,007.91		$1,083.8358	$1,083.84	$1,083.80	$1,083.70