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	$226.41	3.609%	$234.5811	$234.58	$234.60	$234.60
Purchase #2	$138.93	5.516%	$146.5934	$146.59	$146.60	$146.60
Purchase #3	$71.46	6.814%	$76.3293	$76.33	$76.35	$76.30
Purchase #4	$59.67	4.208%	$62.1809	$62.18	$62.20	$62.20
Purchase #5	$136.59	10.110%	$150.3992	$150.40	$150.40	$150.40
Purchase #6	$134.59	13.462%	$152.7085	$152.71	$152.70	$152.70
Purchase #7	$174.50	9.210%	$190.5715	$190.57	$190.55	$190.60
7 purchase totals =	$942.15		$1,013.3639	$1,013.36	$1,013.40	$1,013.40