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	$142.92	7.382%	$153.4704	$153.47	$153.45	$153.50
Purchase #2	$127.50	3.272%	$131.6718	$131.67	$131.65	$131.70
Purchase #3	$200.30	8.478%	$217.2814	$217.28	$217.30	$217.30
Purchase #4	$32.73	7.781%	$35.2767	$35.28	$35.30	$35.30
Purchase #5	$130.25	4.758%	$136.4473	$136.45	$136.45	$136.40
Purchase #6	$203.74	9.317%	$222.7225	$222.72	$222.70	$222.70
Purchase #7	$165.32	8.312%	$179.0614	$179.06	$179.05	$179.10
7 purchase totals =	$1,002.76		$1,075.9315	$1,075.93	$1,075.90	$1,076.00