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	$80.94	10.614%	$89.531	$89.53	$89.55	$89.50
Purchase #2	$34.64	7.191%	$37.131	$37.13	$37.15	$37.10
Purchase #3	$229.83	9.303%	$251.2111	$251.21	$251.20	$251.20
Purchase #4	$207.92	4.321%	$216.9042	$216.90	$216.90	$216.90
Purchase #5	$202.84	3.473%	$209.8846	$209.88	$209.90	$209.90
Purchase #6	$130.86	12.714%	$147.4975	$147.50	$147.50	$147.50
Purchase #7	$69.98	9.168%	$76.3958	$76.40	$76.40	$76.40
7 purchase totals =	$957.01		$1,028.5552	$1,028.55	$1,028.60	$1,028.50