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	$214.66	3.769%	$222.7505	$222.75	$222.75	$222.80
Purchase #2	$103.77	7.746%	$111.808	$111.81	$111.80	$111.80
Purchase #3	$159.58	7.130%	$170.9581	$170.96	$170.95	$171.00
Purchase #4	$135.72	5.192%	$142.7666	$142.77	$142.75	$142.80
Purchase #5	$38.89	12.552%	$43.7715	$43.77	$43.75	$43.80
Purchase #6	$143.90	6.699%	$153.5399	$153.54	$153.55	$153.50
Purchase #7	$72.90	13.217%	$82.5352	$82.54	$82.55	$82.50
7 purchase totals =	$869.42		$928.1298	$928.14	$928.10	$928.20