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	$239.80	10.701%	$265.461	$265.46	$265.45	$265.50
Purchase #2	$47.53	4.185%	$49.5191	$49.52	$49.50	$49.50
Purchase #3	$248.32	13.762%	$282.4938	$282.49	$282.50	$282.50
Purchase #4	$52.46	12.292%	$58.9084	$58.91	$58.90	$58.90
Purchase #5	$241.59	3.696%	$250.5192	$250.52	$250.50	$250.50
Purchase #6	$225.73	11.453%	$251.5829	$251.58	$251.60	$251.60
Purchase #7	$148.75	5.165%	$156.4329	$156.43	$156.45	$156.40
7 purchase totals =	$1,204.18		$1,314.9173	$1,314.91	$1,314.90	$1,314.90