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	$43.79	13.802%	$49.8339	$49.83	$49.85	$49.80
Purchase #2	$101.33	10.515%	$111.9848	$111.98	$112.00	$112.00
Purchase #3	$56.76	12.661%	$63.9464	$63.95	$63.95	$63.90
Purchase #4	$89.85	6.166%	$95.3902	$95.39	$95.40	$95.40
Purchase #5	$211.66	8.356%	$229.3463	$229.35	$229.35	$229.30
Purchase #6	$109.31	6.617%	$116.543	$116.54	$116.55	$116.50
Purchase #7	$19.91	5.850%	$21.0747	$21.07	$21.05	$21.10
7 purchase totals =	$632.61		$688.1193	$688.11	$688.15	$688.00