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	$71.56	11.213%	$79.584	$79.58	$79.60	$79.60
Purchase #2	$221.33	4.690%	$231.7104	$231.71	$231.70	$231.70
Purchase #3	$104.71	13.741%	$119.0982	$119.10	$119.10	$119.10
Purchase #4	$123.41	3.129%	$127.2715	$127.27	$127.25	$127.30
Purchase #5	$134.43	8.666%	$146.0797	$146.08	$146.10	$146.10
Purchase #6	$220.39	3.171%	$227.3786	$227.38	$227.40	$227.40
Purchase #7	$125.82	12.329%	$141.3323	$141.33	$141.35	$141.30
7 purchase totals =	$1,001.65		$1,072.4547	$1,072.45	$1,072.50	$1,072.50