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	$92.47	3.308%	$95.5289	$95.53	$95.55	$95.50
Purchase #2	$160.64	3.111%	$165.6375	$165.64	$165.65	$165.60
Purchase #3	$103.34	10.872%	$114.5751	$114.58	$114.60	$114.60
Purchase #4	$249.83	12.654%	$281.4435	$281.44	$281.45	$281.40
Purchase #5	$162.97	4.320%	$170.0103	$170.01	$170.00	$170.00
Purchase #6	$34.95	13.342%	$39.613	$39.61	$39.60	$39.60
Purchase #7	$194.73	11.688%	$217.49	$217.49	$217.50	$217.50
7 purchase totals =	$998.93		$1,084.2983	$1,084.30	$1,084.35	$1,084.20