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	$85.99	4.504%	$89.863	$89.86	$89.85	$89.90
Purchase #2	$248.27	10.328%	$273.9113	$273.91	$273.90	$273.90
Purchase #3	$135.47	4.399%	$141.4293	$141.43	$141.45	$141.40
Purchase #4	$40.58	13.163%	$45.9215	$45.92	$45.90	$45.90
Purchase #5	$49.64	8.257%	$53.7388	$53.74	$53.75	$53.70
Purchase #6	$61.46	3.725%	$63.7494	$63.75	$63.75	$63.70
Purchase #7	$166.99	11.614%	$186.3842	$186.38	$186.40	$186.40
7 purchase totals =	$788.40		$854.9975	$854.99	$855.00	$854.90