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	$234.78	4.317%	$244.9155	$244.92	$244.90	$244.90
Purchase #2	$184.68	3.874%	$191.8345	$191.83	$191.85	$191.80
Purchase #3	$96.30	13.289%	$109.0973	$109.10	$109.10	$109.10
Purchase #4	$94.83	11.403%	$105.6435	$105.64	$105.65	$105.60
Purchase #5	$125.54	10.534%	$138.7644	$138.76	$138.75	$138.80
Purchase #6	$184.90	6.312%	$196.5709	$196.57	$196.55	$196.60
Purchase #7	$12.25	11.602%	$13.6712	$13.67	$13.65	$13.70
7 purchase totals =	$933.28		$1,000.4973	$1,000.49	$1,000.45	$1,000.50