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	$75.35	10.768%	$83.4637	$83.46	$83.45	$83.50
Purchase #2	$33.48	10.795%	$37.0942	$37.09	$37.10	$37.10
Purchase #3	$90.81	8.837%	$98.8349	$98.83	$98.85	$98.80
Purchase #4	$250.83	4.787%	$262.8372	$262.84	$262.85	$262.80
Purchase #5	$64.91	10.576%	$71.7749	$71.77	$71.75	$71.80
Purchase #6	$173.53	4.700%	$181.6859	$181.69	$181.70	$181.70
Purchase #7	$199.26	11.566%	$222.3064	$222.31	$222.30	$222.30
7 purchase totals =	$888.17		$957.9972	$957.99	$958.00	$958.00