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	$171.85	3.713%	$178.2308	$178.23	$178.25	$178.20
Purchase #2	$179.77	3.420%	$185.9181	$185.92	$185.90	$185.90
Purchase #3	$186.77	4.468%	$195.1149	$195.11	$195.10	$195.10
Purchase #4	$31.43	13.470%	$35.6636	$35.66	$35.65	$35.70
Purchase #5	$136.43	7.346%	$146.4521	$146.45	$146.45	$146.50
Purchase #6	$96.81	4.208%	$100.8838	$100.88	$100.90	$100.90
Purchase #7	$11.79	12.225%	$13.2313	$13.23	$13.25	$13.20
7 purchase totals =	$814.85		$855.4946	$855.48	$855.50	$855.50