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	$198.52	11.632%	$221.6118	$221.61	$221.60	$221.60
Purchase #2	$70.62	13.850%	$80.4009	$80.40	$80.40	$80.40
Purchase #3	$185.78	5.275%	$195.5799	$195.58	$195.60	$195.60
Purchase #4	$75.67	12.375%	$85.0342	$85.03	$85.05	$85.00
Purchase #5	$244.36	7.516%	$262.7261	$262.73	$262.75	$262.70
Purchase #6	$126.80	13.659%	$144.1196	$144.12	$144.10	$144.10
Purchase #7	$115.37	10.550%	$127.5415	$127.54	$127.55	$127.50
7 purchase totals =	$1,017.12		$1,117.0140	$1,117.01	$1,117.05	$1,116.90