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	$191.88	7.642%	$206.5435	$206.54	$206.55	$206.50
Purchase #2	$56.53	4.653%	$59.1603	$59.16	$59.15	$59.20
Purchase #3	$188.56	6.255%	$200.3544	$200.35	$200.35	$200.40
Purchase #4	$13.98	8.478%	$15.1652	$15.17	$15.15	$15.20
Purchase #5	$177.42	4.183%	$184.8415	$184.84	$184.85	$184.80
Purchase #6	$213.46	11.818%	$238.6867	$238.69	$238.70	$238.70
Purchase #7	$13.55	9.624%	$14.8541	$14.85	$14.85	$14.90
7 purchase totals =	$855.38		$919.6057	$919.60	$919.60	$919.70