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	$72.76	12.170%	$81.6149	$81.61	$81.60	$81.60
Purchase #2	$171.63	13.321%	$194.4928	$194.49	$194.50	$194.50
Purchase #3	$30.47	5.523%	$32.1529	$32.15	$32.15	$32.20
Purchase #4	$153.44	4.698%	$160.6486	$160.65	$160.65	$160.60
Purchase #5	$170.64	9.313%	$186.5317	$186.53	$186.55	$186.50
Purchase #6	$100.86	4.645%	$105.5449	$105.54	$105.55	$105.50
Purchase #7	$52.85	12.445%	$59.4272	$59.43	$59.45	$59.40
7 purchase totals =	$752.65		$820.4130	$820.40	$820.45	$820.30