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	$196.34	6.236%	$208.5838	$208.58	$208.60	$208.60
Purchase #2	$180.82	3.741%	$187.5845	$187.58	$187.60	$187.60
Purchase #3	$60.82	9.124%	$66.3692	$66.37	$66.35	$66.40
Purchase #4	$53.78	10.228%	$59.2806	$59.28	$59.30	$59.30
Purchase #5	$29.74	4.236%	$30.9998	$31.00	$31.00	$31.00
Purchase #6	$20.39	9.550%	$22.3372	$22.34	$22.35	$22.30
Purchase #7	$217.66	7.347%	$233.6515	$233.65	$233.65	$233.70
7 purchase totals =	$759.55		$808.8066	$808.80	$808.85	$808.90