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	$213.50	9.195%	$233.1313	$233.13	$233.15	$233.10
Purchase #2	$222.98	4.641%	$233.3285	$233.33	$233.35	$233.30
Purchase #3	$60.90	5.119%	$64.0175	$64.02	$64.00	$64.00
Purchase #4	$154.41	8.858%	$168.0876	$168.09	$168.10	$168.10
Purchase #5	$36.30	11.617%	$40.517	$40.52	$40.50	$40.50
Purchase #6	$89.46	9.117%	$97.6161	$97.62	$97.60	$97.60
Purchase #7	$150.30	6.123%	$159.5029	$159.50	$159.50	$159.50
7 purchase totals =	$927.85		$996.2009	$996.21	$996.20	$996.10