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	$69.68	13.233%	$78.9008	$78.90	$78.90	$78.90
Purchase #2	$146.92	9.283%	$160.5586	$160.56	$160.55	$160.60
Purchase #3	$121.88	3.302%	$125.9045	$125.90	$125.90	$125.90
Purchase #4	$178.30	7.470%	$191.619	$191.62	$191.60	$191.60
Purchase #5	$105.50	11.397%	$117.5238	$117.52	$117.50	$117.50
Purchase #6	$40.54	3.626%	$42.01	$42.01	$42.00	$42.00
Purchase #7	$207.91	6.623%	$221.6799	$221.68	$221.70	$221.70
7 purchase totals =	$870.73		$938.1966	$938.19	$938.15	$938.20