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	$200.39	11.420%	$223.2745	$223.27	$223.25	$223.30
Purchase #2	$48.47	8.553%	$52.6156	$52.62	$52.60	$52.60
Purchase #3	$119.54	7.492%	$128.4959	$128.50	$128.50	$128.50
Purchase #4	$159.30	5.236%	$167.6409	$167.64	$167.65	$167.60
Purchase #5	$184.64	10.237%	$203.5416	$203.54	$203.55	$203.50
Purchase #6	$233.55	11.710%	$260.8987	$260.90	$260.90	$260.90
Purchase #7	$71.62	12.167%	$80.334	$80.33	$80.35	$80.30
7 purchase totals =	$1,017.51		$1,116.8012	$1,116.80	$1,116.80	$1,116.70