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	$176.72	9.181%	$192.9447	$192.94	$192.95	$192.90
Purchase #2	$53.56	9.122%	$58.4457	$58.45	$58.45	$58.40
Purchase #3	$89.38	10.367%	$98.646	$98.65	$98.65	$98.60
Purchase #4	$78.43	3.740%	$81.3633	$81.36	$81.35	$81.40
Purchase #5	$205.89	4.688%	$215.5421	$215.54	$215.55	$215.50
Purchase #6	$84.97	5.475%	$89.6221	$89.62	$89.60	$89.60
Purchase #7	$38.34	10.558%	$42.3879	$42.39	$42.40	$42.40
7 purchase totals =	$727.29		$778.9518	$778.95	$778.95	$778.80