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	$97.61	4.727%	$102.224	$102.22	$102.20	$102.20
Purchase #2	$172.78	10.718%	$191.2986	$191.30	$191.30	$191.30
Purchase #3	$20.92	4.108%	$21.7794	$21.78	$21.80	$21.80
Purchase #4	$91.38	3.286%	$94.3827	$94.38	$94.40	$94.40
Purchase #5	$216.60	4.270%	$225.8488	$225.85	$225.85	$225.80
Purchase #6	$227.90	6.310%	$242.2805	$242.28	$242.30	$242.30
Purchase #7	$12.78	13.484%	$14.5033	$14.50	$14.50	$14.50
7 purchase totals =	$839.97		$892.3173	$892.31	$892.35	$892.30