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	$213.95	11.418%	$238.3788	$238.38	$238.40	$238.40
Purchase #2	$222.61	6.773%	$237.6874	$237.69	$237.70	$237.70
Purchase #3	$57.89	8.464%	$62.7898	$62.79	$62.80	$62.80
Purchase #4	$41.67	8.383%	$45.1632	$45.16	$45.15	$45.20
Purchase #5	$239.38	7.854%	$258.1809	$258.18	$258.20	$258.20
Purchase #6	$97.64	8.247%	$105.6924	$105.69	$105.70	$105.70
Purchase #7	$72.35	8.361%	$78.3992	$78.40	$78.40	$78.40
7 purchase totals =	$945.49		$1,026.2917	$1,026.29	$1,026.35	$1,026.40