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	$54.46	10.124%	$59.9735	$59.97	$59.95	$60.00
Purchase #2	$186.61	5.468%	$196.8138	$196.81	$196.80	$196.80
Purchase #3	$117.62	3.119%	$121.2886	$121.29	$121.30	$121.30
Purchase #4	$242.52	6.596%	$258.5166	$258.52	$258.50	$258.50
Purchase #5	$76.90	11.259%	$85.5582	$85.56	$85.55	$85.60
Purchase #6	$132.58	6.758%	$141.5398	$141.54	$141.55	$141.50
Purchase #7	$133.57	11.252%	$148.5993	$148.60	$148.60	$148.60
7 purchase totals =	$944.26		$1,012.2898	$1,012.29	$1,012.25	$1,012.30