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	$117.28	12.247%	$131.6433	$131.64	$131.65	$131.60
Purchase #2	$77.89	4.203%	$81.1637	$81.16	$81.15	$81.20
Purchase #3	$91.79	8.195%	$99.3122	$99.31	$99.30	$99.30
Purchase #4	$241.63	11.571%	$269.589	$269.59	$269.60	$269.60
Purchase #5	$91.57	12.292%	$102.8258	$102.83	$102.85	$102.80
Purchase #6	$82.55	8.335%	$89.4305	$89.43	$89.45	$89.40
Purchase #7	$145.42	4.583%	$152.0846	$152.08	$152.10	$152.10
7 purchase totals =	$848.13		$926.0491	$926.04	$926.10	$926.00