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	$158.59	9.607%	$173.8257	$173.83	$173.85	$173.80
Purchase #2	$168.48	11.856%	$188.455	$188.46	$188.45	$188.50
Purchase #3	$86.86	5.487%	$91.626	$91.63	$91.65	$91.60
Purchase #4	$202.49	9.136%	$220.9895	$220.99	$221.00	$221.00
Purchase #5	$22.41	10.564%	$24.7774	$24.78	$24.80	$24.80
Purchase #6	$249.78	4.665%	$261.4322	$261.43	$261.45	$261.40
Purchase #7	$148.76	9.384%	$162.7196	$162.72	$162.70	$162.70
7 purchase totals =	$1,037.37		$1,123.8254	$1,123.84	$1,123.90	$1,123.80