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	$145.92	10.660%	$161.4751	$161.48	$161.50	$161.50
Purchase #2	$213.25	7.147%	$228.491	$228.49	$228.50	$228.50
Purchase #3	$138.46	12.384%	$155.6069	$155.61	$155.60	$155.60
Purchase #4	$186.70	7.211%	$200.1629	$200.16	$200.15	$200.20
Purchase #5	$175.87	8.545%	$190.8981	$190.90	$190.90	$190.90
Purchase #6	$28.59	10.378%	$31.5571	$31.56	$31.55	$31.60
Purchase #7	$110.30	6.557%	$117.5324	$117.53	$117.55	$117.50
7 purchase totals =	$999.09		$1,085.7235	$1,085.73	$1,085.75	$1,085.80