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	$144.67	9.623%	$158.5916	$158.59	$158.60	$158.60
Purchase #2	$216.72	3.293%	$223.8566	$223.86	$223.85	$223.90
Purchase #3	$209.46	5.600%	$221.1898	$221.19	$221.20	$221.20
Purchase #4	$250.45	12.578%	$281.9516	$281.95	$281.95	$282.00
Purchase #5	$166.88	9.550%	$182.817	$182.82	$182.80	$182.80
Purchase #6	$190.35	3.204%	$196.4488	$196.45	$196.45	$196.40
Purchase #7	$40.82	7.449%	$43.8607	$43.86	$43.85	$43.90
7 purchase totals =	$1,219.35		$1,308.7161	$1,308.72	$1,308.70	$1,308.80