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	$179.91	6.287%	$191.2209	$191.22	$191.20	$191.20
Purchase #2	$23.29	13.131%	$26.3482	$26.35	$26.35	$26.30
Purchase #3	$135.62	6.754%	$144.7798	$144.78	$144.80	$144.80
Purchase #4	$31.33	7.825%	$33.7816	$33.78	$33.80	$33.80
Purchase #5	$237.89	10.358%	$262.5306	$262.53	$262.55	$262.50
Purchase #6	$164.80	8.250%	$178.396	$178.40	$178.40	$178.40
Purchase #7	$63.95	11.808%	$71.5012	$71.50	$71.50	$71.50
7 purchase totals =	$836.79		$908.5583	$908.56	$908.60	$908.50