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	$155.57	4.681%	$162.8522	$162.85	$162.85	$162.90
Purchase #2	$194.88	11.654%	$217.5913	$217.59	$217.60	$217.60
Purchase #3	$65.58	7.508%	$70.5037	$70.50	$70.50	$70.50
Purchase #4	$150.32	12.871%	$169.6677	$169.67	$169.65	$169.70
Purchase #5	$51.71	12.165%	$58.0005	$58.00	$58.00	$58.00
Purchase #6	$152.50	3.806%	$158.3042	$158.30	$158.30	$158.30
Purchase #7	$136.73	6.437%	$145.5313	$145.53	$145.55	$145.50
7 purchase totals =	$907.29		$982.4509	$982.44	$982.45	$982.50