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	$77.54	5.716%	$81.9722	$81.97	$81.95	$82.00
Purchase #2	$108.54	3.144%	$111.9525	$111.95	$111.95	$112.00
Purchase #3	$250.63	11.768%	$280.1241	$280.12	$280.10	$280.10
Purchase #4	$140.81	10.480%	$155.5669	$155.57	$155.55	$155.60
Purchase #5	$64.53	4.114%	$67.1848	$67.18	$67.20	$67.20
Purchase #6	$236.73	10.395%	$261.3381	$261.34	$261.35	$261.30
Purchase #7	$58.28	12.846%	$65.7666	$65.77	$65.75	$65.80
7 purchase totals =	$937.06		$1,023.9052	$1,023.90	$1,023.85	$1,024.00