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	$69.57	5.666%	$73.5118	$73.51	$73.50	$73.50
Purchase #2	$10.84	11.383%	$12.0739	$12.07	$12.05	$12.10
Purchase #3	$28.57	10.183%	$31.4793	$31.48	$31.50	$31.50
Purchase #4	$49.55	10.424%	$54.7151	$54.72	$54.70	$54.70
Purchase #5	$14.79	6.783%	$15.7932	$15.79	$15.80	$15.80
Purchase #6	$153.46	7.388%	$164.7976	$164.80	$164.80	$164.80
Purchase #7	$165.79	12.116%	$185.8771	$185.88	$185.90	$185.90
7 purchase totals =	$492.57		$538.2480	$538.25	$538.25	$538.30