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	$248.58	7.656%	$267.6113	$267.61	$267.60	$267.60
Purchase #2	$95.85	4.748%	$100.401	$100.40	$100.40	$100.40
Purchase #3	$17.41	5.719%	$18.4057	$18.41	$18.40	$18.40
Purchase #4	$176.98	7.432%	$190.1332	$190.13	$190.15	$190.10
Purchase #5	$207.91	6.517%	$221.4595	$221.46	$221.45	$221.50
Purchase #6	$243.75	5.681%	$257.5974	$257.60	$257.60	$257.60
Purchase #7	$36.66	4.496%	$38.3082	$38.31	$38.30	$38.30
7 purchase totals =	$1,027.14		$1,093.9163	$1,093.92	$1,093.90	$1,093.90