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	$242.39	9.375%	$265.1141	$265.11	$265.10	$265.10
Purchase #2	$162.69	9.317%	$177.8478	$177.85	$177.85	$177.80
Purchase #3	$77.40	4.303%	$80.7305	$80.73	$80.75	$80.70
Purchase #4	$40.68	4.705%	$42.594	$42.59	$42.60	$42.60
Purchase #5	$212.52	3.734%	$220.4555	$220.46	$220.45	$220.50
Purchase #6	$45.61	13.474%	$51.7555	$51.76	$51.75	$51.80
Purchase #7	$168.72	5.471%	$177.9507	$177.95	$177.95	$178.00
7 purchase totals =	$950.01		$1,016.4481	$1,016.45	$1,016.45	$1,016.50