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	$190.88	11.584%	$212.9915	$212.99	$213.00	$213.00
Purchase #2	$174.39	10.856%	$193.3218	$193.32	$193.30	$193.30
Purchase #3	$161.64	4.131%	$168.3173	$168.32	$168.30	$168.30
Purchase #4	$39.77	9.327%	$43.4793	$43.48	$43.50	$43.50
Purchase #5	$23.50	4.209%	$24.4891	$24.49	$24.50	$24.50
Purchase #6	$53.55	5.581%	$56.5386	$56.54	$56.55	$56.50
Purchase #7	$49.36	6.123%	$52.3823	$52.38	$52.40	$52.40
7 purchase totals =	$693.09		$751.5199	$751.52	$751.55	$751.50