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	$53.64	10.706%	$59.3827	$59.38	$59.40	$59.40
Purchase #2	$50.81	4.322%	$53.006	$53.01	$53.00	$53.00
Purchase #3	$231.34	11.763%	$258.5525	$258.55	$258.55	$258.60
Purchase #4	$224.67	12.637%	$253.0615	$253.06	$253.05	$253.10
Purchase #5	$13.70	6.629%	$14.6082	$14.61	$14.60	$14.60
Purchase #6	$229.48	7.705%	$247.1614	$247.16	$247.15	$247.20
Purchase #7	$142.84	6.282%	$151.8132	$151.81	$151.80	$151.80
7 purchase totals =	$946.48		$1,037.5855	$1,037.58	$1,037.55	$1,037.70