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	$77.86	9.383%	$85.1656	$85.17	$85.15	$85.20
Purchase #2	$239.59	9.459%	$262.2528	$262.25	$262.25	$262.30
Purchase #3	$47.51	12.473%	$53.4359	$53.44	$53.45	$53.40
Purchase #4	$241.71	8.279%	$261.7212	$261.72	$261.70	$261.70
Purchase #5	$138.50	10.139%	$152.5425	$152.54	$152.55	$152.50
Purchase #6	$27.75	12.467%	$31.2096	$31.21	$31.20	$31.20
Purchase #7	$241.70	6.533%	$257.4903	$257.49	$257.50	$257.50
7 purchase totals =	$1,014.62		$1,103.8179	$1,103.82	$1,103.80	$1,103.80