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	$187.76	3.798%	$194.8911	$194.89	$194.90	$194.90
Purchase #2	$184.78	6.551%	$196.8849	$196.88	$196.90	$196.90
Purchase #3	$235.68	4.146%	$245.4513	$245.45	$245.45	$245.50
Purchase #4	$99.84	12.136%	$111.9566	$111.96	$111.95	$112.00
Purchase #5	$23.85	5.517%	$25.1658	$25.17	$25.15	$25.20
Purchase #6	$32.88	7.555%	$35.3641	$35.36	$35.35	$35.40
Purchase #7	$63.49	3.181%	$65.5096	$65.51	$65.50	$65.50
7 purchase totals =	$828.28		$875.2234	$875.22	$875.20	$875.40