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	$152.88	13.556%	$173.6044	$173.60	$173.60	$173.60
Purchase #2	$89.41	8.832%	$97.3067	$97.31	$97.30	$97.30
Purchase #3	$241.93	8.838%	$263.3118	$263.31	$263.30	$263.30
Purchase #4	$137.53	10.612%	$152.1247	$152.12	$152.10	$152.10
Purchase #5	$75.39	9.207%	$82.3312	$82.33	$82.35	$82.30
Purchase #6	$100.47	10.437%	$110.9561	$110.96	$110.95	$111.00
Purchase #7	$192.64	3.689%	$199.7465	$199.75	$199.75	$199.70
7 purchase totals =	$990.25		$1,079.3814	$1,079.38	$1,079.35	$1,079.30