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	$80.34	6.513%	$85.5725	$85.57	$85.55	$85.60
Purchase #2	$160.53	3.225%	$165.7071	$165.71	$165.70	$165.70
Purchase #3	$101.60	7.739%	$109.4628	$109.46	$109.45	$109.50
Purchase #4	$134.74	12.791%	$151.9746	$151.97	$151.95	$152.00
Purchase #5	$85.75	5.862%	$90.7767	$90.78	$90.80	$90.80
Purchase #6	$177.75	10.361%	$196.1667	$196.17	$196.15	$196.20
Purchase #7	$240.95	4.677%	$252.2192	$252.22	$252.20	$252.20
7 purchase totals =	$981.66		$1,051.8796	$1,051.88	$1,051.80	$1,052.00