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	$205.57	3.359%	$212.4751	$212.48	$212.50	$212.50
Purchase #2	$150.88	7.677%	$162.4631	$162.46	$162.45	$162.50
Purchase #3	$181.40	5.108%	$190.6659	$190.67	$190.65	$190.70
Purchase #4	$76.44	7.843%	$82.4352	$82.44	$82.45	$82.40
Purchase #5	$196.78	13.653%	$223.6464	$223.65	$223.65	$223.60
Purchase #6	$215.86	8.114%	$233.3749	$233.37	$233.35	$233.40
Purchase #7	$211.71	4.358%	$220.9363	$220.94	$220.95	$220.90
7 purchase totals =	$1,238.64		$1,325.9969	$1,326.01	$1,326.00	$1,326.00