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	$249.65	5.453%	$263.2634	$263.26	$263.25	$263.30
Purchase #2	$75.51	12.682%	$85.0862	$85.09	$85.10	$85.10
Purchase #3	$114.83	3.564%	$118.9225	$118.92	$118.90	$118.90
Purchase #4	$157.27	9.749%	$172.6023	$172.60	$172.60	$172.60
Purchase #5	$216.49	12.536%	$243.6292	$243.63	$243.65	$243.60
Purchase #6	$137.84	3.521%	$142.6933	$142.69	$142.70	$142.70
Purchase #7	$68.36	6.671%	$72.9203	$72.92	$72.90	$72.90
7 purchase totals =	$1,019.95		$1,099.1172	$1,099.11	$1,099.10	$1,099.10