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	$150.86	10.727%	$167.0428	$167.04	$167.05	$167.00
Purchase #2	$172.54	7.846%	$186.0775	$186.08	$186.10	$186.10
Purchase #3	$17.79	10.399%	$19.64	$19.64	$19.65	$19.60
Purchase #4	$121.38	13.576%	$137.8585	$137.86	$137.85	$137.90
Purchase #5	$134.94	5.597%	$142.4926	$142.49	$142.50	$142.50
Purchase #6	$58.83	6.284%	$62.5269	$62.53	$62.55	$62.50
Purchase #7	$151.86	11.581%	$169.4469	$169.45	$169.45	$169.40
7 purchase totals =	$808.20		$885.0852	$885.09	$885.15	$885.00