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	$204.90	13.377%	$232.3095	$232.31	$232.30	$232.30
Purchase #2	$175.42	12.109%	$196.6616	$196.66	$196.65	$196.70
Purchase #3	$215.77	12.353%	$242.4241	$242.42	$242.40	$242.40
Purchase #4	$6.38	5.712%	$6.7444	$6.74	$6.75	$6.70
Purchase #5	$132.97	13.382%	$150.764	$150.76	$150.75	$150.80
Purchase #6	$131.31	9.107%	$143.2684	$143.27	$143.25	$143.30
Purchase #7	$148.82	13.202%	$168.4672	$168.47	$168.45	$168.50
7 purchase totals =	$1,015.57		$1,140.6392	$1,140.63	$1,140.55	$1,140.70