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	$92.87	9.715%	$101.8923	$101.89	$101.90	$101.90
Purchase #2	$93.54	12.228%	$104.9781	$104.98	$105.00	$105.00
Purchase #3	$230.98	12.279%	$259.342	$259.34	$259.35	$259.30
Purchase #4	$59.64	10.673%	$66.0054	$66.01	$66.00	$66.00
Purchase #5	$240.38	6.223%	$255.3388	$255.34	$255.35	$255.30
Purchase #6	$80.77	10.574%	$89.3106	$89.31	$89.30	$89.30
Purchase #7	$236.27	10.273%	$260.542	$260.54	$260.55	$260.50
7 purchase totals =	$1,034.45		$1,137.4092	$1,137.41	$1,137.45	$1,137.30