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	$102.32	10.354%	$112.9142	$112.91	$112.90	$112.90
Purchase #2	$58.36	8.298%	$63.2027	$63.20	$63.20	$63.20
Purchase #3	$116.33	12.837%	$131.2633	$131.26	$131.25	$131.30
Purchase #4	$192.83	7.477%	$207.2479	$207.25	$207.25	$207.20
Purchase #5	$226.98	11.734%	$253.6138	$253.61	$253.60	$253.60
Purchase #6	$208.98	11.510%	$233.0336	$233.03	$233.05	$233.00
Purchase #7	$39.33	10.168%	$43.3291	$43.33	$43.35	$43.30
7 purchase totals =	$945.13		$1,044.6046	$1,044.59	$1,044.60	$1,044.50