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	$80.39	13.106%	$90.9259	$90.93	$90.95	$90.90
Purchase #2	$173.74	6.637%	$185.2711	$185.27	$185.25	$185.30
Purchase #3	$6.77	10.480%	$7.4795	$7.48	$7.50	$7.50
Purchase #4	$150.96	7.564%	$162.3786	$162.38	$162.40	$162.40
Purchase #5	$8.82	8.330%	$9.5547	$9.55	$9.55	$9.60
Purchase #6	$128.68	10.246%	$141.8646	$141.86	$141.85	$141.90
Purchase #7	$26.27	9.450%	$28.7525	$28.75	$28.75	$28.80
7 purchase totals =	$575.63		$626.2269	$626.22	$626.25	$626.40