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	$226.52	4.226%	$236.0927	$236.09	$236.10	$236.10
Purchase #2	$83.51	8.353%	$90.4856	$90.49	$90.50	$90.50
Purchase #3	$186.97	8.375%	$202.6287	$202.63	$202.65	$202.60
Purchase #4	$42.75	10.573%	$47.27	$47.27	$47.25	$47.30
Purchase #5	$54.36	9.659%	$59.6106	$59.61	$59.60	$59.60
Purchase #6	$131.38	6.628%	$140.0879	$140.09	$140.10	$140.10
Purchase #7	$247.60	11.337%	$275.6704	$275.67	$275.65	$275.70
7 purchase totals =	$973.09		$1,051.8459	$1,051.85	$1,051.85	$1,051.90