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	$208.93	4.450%	$218.2274	$218.23	$218.25	$218.20
Purchase #2	$174.67	12.281%	$196.1212	$196.12	$196.10	$196.10
Purchase #3	$170.85	9.716%	$187.4498	$187.45	$187.45	$187.40
Purchase #4	$48.85	6.305%	$51.93	$51.93	$51.95	$51.90
Purchase #5	$40.37	5.703%	$42.6723	$42.67	$42.65	$42.70
Purchase #6	$35.36	6.470%	$37.6478	$37.65	$37.65	$37.60
Purchase #7	$250.72	13.115%	$283.6019	$283.60	$283.60	$283.60
7 purchase totals =	$929.75		$1,017.6504	$1,017.65	$1,017.65	$1,017.50