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	$184.43	13.270%	$208.9039	$208.90	$208.90	$208.90
Purchase #2	$223.58	6.523%	$238.1641	$238.16	$238.15	$238.20
Purchase #3	$10.91	13.803%	$12.4159	$12.42	$12.40	$12.40
Purchase #4	$130.48	3.369%	$134.8759	$134.88	$134.90	$134.90
Purchase #5	$88.98	12.354%	$99.9726	$99.97	$99.95	$100.00
Purchase #6	$237.88	13.699%	$270.4672	$270.47	$270.45	$270.50
Purchase #7	$85.46	3.694%	$88.6169	$88.62	$88.60	$88.60
7 purchase totals =	$961.72		$1,053.4165	$1,053.42	$1,053.35	$1,053.50