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	$77.27	10.685%	$85.5263	$85.53	$85.55	$85.50
Purchase #2	$195.95	11.665%	$218.8076	$218.81	$218.80	$218.80
Purchase #3	$211.85	3.688%	$219.663	$219.66	$219.65	$219.70
Purchase #4	$102.59	11.171%	$114.0503	$114.05	$114.05	$114.10
Purchase #5	$54.29	9.813%	$59.6175	$59.62	$59.60	$59.60
Purchase #6	$56.87	10.475%	$62.8271	$62.83	$62.85	$62.80
Purchase #7	$208.95	5.689%	$220.8372	$220.84	$220.85	$220.80
7 purchase totals =	$907.77		$981.3290	$981.34	$981.35	$981.30