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	$43.84	13.172%	$49.6146	$49.61	$49.60	$49.60
Purchase #2	$40.38	6.119%	$42.8509	$42.85	$42.85	$42.90
Purchase #3	$9.81	5.105%	$10.3108	$10.31	$10.30	$10.30
Purchase #4	$239.35	6.627%	$255.2117	$255.21	$255.20	$255.20
Purchase #5	$223.84	10.520%	$247.388	$247.39	$247.40	$247.40
Purchase #6	$219.35	6.375%	$233.3336	$233.33	$233.35	$233.30
Purchase #7	$82.70	6.417%	$88.0069	$88.01	$88.00	$88.00
7 purchase totals =	$859.27		$926.7165	$926.71	$926.70	$926.70