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	$191.93	4.565%	$200.6916	$200.69	$200.70	$200.70
Purchase #2	$59.98	10.657%	$66.3721	$66.37	$66.35	$66.40
Purchase #3	$183.81	8.596%	$199.6103	$199.61	$199.60	$199.60
Purchase #4	$23.58	7.419%	$25.3294	$25.33	$25.35	$25.30
Purchase #5	$125.66	13.419%	$142.5223	$142.52	$142.50	$142.50
Purchase #6	$56.93	4.300%	$59.378	$59.38	$59.40	$59.40
Purchase #7	$249.77	4.545%	$261.122	$261.12	$261.10	$261.10
7 purchase totals =	$891.66		$955.0257	$955.02	$955.00	$955.00