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	$238.90	11.149%	$265.535	$265.54	$265.55	$265.50
Purchase #2	$97.70	13.779%	$111.1621	$111.16	$111.15	$111.20
Purchase #3	$62.99	9.760%	$69.1378	$69.14	$69.15	$69.10
Purchase #4	$77.76	9.843%	$85.4139	$85.41	$85.40	$85.40
Purchase #5	$31.25	13.384%	$35.4325	$35.43	$35.45	$35.40
Purchase #6	$10.28	9.238%	$11.2297	$11.23	$11.25	$11.20
Purchase #7	$115.74	6.293%	$123.0235	$123.02	$123.00	$123.00
7 purchase totals =	$634.62		$700.9345	$700.93	$700.95	$700.80