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	$151.45	7.323%	$162.5407	$162.54	$162.55	$162.50
Purchase #2	$143.70	5.812%	$152.0518	$152.05	$152.05	$152.10
Purchase #3	$245.33	5.701%	$259.3163	$259.32	$259.30	$259.30
Purchase #4	$232.91	4.154%	$242.5851	$242.59	$242.60	$242.60
Purchase #5	$189.65	13.646%	$215.5296	$215.53	$215.55	$215.50
Purchase #6	$234.45	10.264%	$258.5139	$258.51	$258.50	$258.50
Purchase #7	$184.58	7.495%	$198.4143	$198.41	$198.40	$198.40
7 purchase totals =	$1,382.07		$1,488.9517	$1,488.95	$1,488.95	$1,488.90