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	$156.48	13.335%	$177.3466	$177.35	$177.35	$177.30
Purchase #2	$96.89	6.562%	$103.2479	$103.25	$103.25	$103.20
Purchase #3	$245.39	6.298%	$260.8447	$260.84	$260.85	$260.80
Purchase #4	$162.38	13.687%	$184.605	$184.61	$184.60	$184.60
Purchase #5	$90.63	11.724%	$101.2555	$101.26	$101.25	$101.30
Purchase #6	$52.28	3.569%	$54.1459	$54.15	$54.15	$54.10
Purchase #7	$128.44	10.314%	$141.6873	$141.69	$141.70	$141.70
7 purchase totals =	$932.49		$1,023.1329	$1,023.15	$1,023.15	$1,023.00