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	$48.29	5.470%	$50.9315	$50.93	$50.95	$50.90
Purchase #2	$18.43	8.745%	$20.0417	$20.04	$20.05	$20.00
Purchase #3	$170.67	4.622%	$178.5584	$178.56	$178.55	$178.60
Purchase #4	$250.93	13.820%	$285.6085	$285.61	$285.60	$285.60
Purchase #5	$238.97	11.459%	$266.3536	$266.35	$266.35	$266.40
Purchase #6	$35.57	13.461%	$40.3581	$40.36	$40.35	$40.40
Purchase #7	$57.39	7.821%	$61.8785	$61.88	$61.90	$61.90
7 purchase totals =	$820.25		$903.7303	$903.73	$903.75	$903.80