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	$131.97	9.382%	$144.3514	$144.35	$144.35	$144.40
Purchase #2	$73.64	6.836%	$78.674	$78.67	$78.65	$78.70
Purchase #3	$69.87	6.734%	$74.575	$74.58	$74.60	$74.60
Purchase #4	$196.27	11.805%	$219.4397	$219.44	$219.45	$219.40
Purchase #5	$250.51	6.336%	$266.3823	$266.38	$266.40	$266.40
Purchase #6	$6.73	12.153%	$7.5479	$7.55	$7.55	$7.50
Purchase #7	$130.84	7.248%	$140.3233	$140.32	$140.30	$140.30
7 purchase totals =	$859.83		$931.2936	$931.29	$931.30	$931.30