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	$161.28	7.181%	$172.8615	$172.86	$172.85	$172.90
Purchase #2	$71.62	10.214%	$78.9353	$78.94	$78.95	$78.90
Purchase #3	$39.82	6.465%	$42.3944	$42.39	$42.40	$42.40
Purchase #4	$16.68	7.794%	$17.98	$17.98	$18.00	$18.00
Purchase #5	$195.85	8.524%	$212.5443	$212.54	$212.55	$212.50
Purchase #6	$183.97	6.758%	$196.4027	$196.40	$196.40	$196.40
Purchase #7	$59.94	3.553%	$62.0697	$62.07	$62.05	$62.10
7 purchase totals =	$729.16		$783.1879	$783.18	$783.20	$783.20