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	$53.97	4.612%	$56.4591	$56.46	$56.45	$56.50
Purchase #2	$139.29	10.590%	$154.0408	$154.04	$154.05	$154.00
Purchase #3	$159.65	12.829%	$180.1315	$180.13	$180.15	$180.10
Purchase #4	$196.50	6.629%	$209.526	$209.53	$209.55	$209.50
Purchase #5	$242.66	8.149%	$262.4344	$262.43	$262.45	$262.40
Purchase #6	$82.75	9.245%	$90.4002	$90.40	$90.40	$90.40
Purchase #7	$193.34	11.535%	$215.6418	$215.64	$215.65	$215.60
7 purchase totals =	$1,068.16		$1,168.6338	$1,168.63	$1,168.70	$1,168.50