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	$52.81	9.479%	$57.8159	$57.82	$57.80	$57.80
Purchase #2	$55.64	13.825%	$63.3322	$63.33	$63.35	$63.30
Purchase #3	$69.28	4.756%	$72.575	$72.58	$72.60	$72.60
Purchase #4	$99.44	12.608%	$111.9774	$111.98	$112.00	$112.00
Purchase #5	$228.40	11.146%	$253.8575	$253.86	$253.85	$253.90
Purchase #6	$81.68	5.465%	$86.1438	$86.14	$86.15	$86.10
Purchase #7	$102.58	13.146%	$116.0652	$116.07	$116.05	$116.10
7 purchase totals =	$689.83		$761.7670	$761.78	$761.80	$761.80