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	$217.97	11.331%	$242.6682	$242.67	$242.65	$242.70
Purchase #2	$201.25	4.590%	$210.4874	$210.49	$210.50	$210.50
Purchase #3	$190.51	3.152%	$196.5149	$196.51	$196.50	$196.50
Purchase #4	$105.32	6.697%	$112.3733	$112.37	$112.35	$112.40
Purchase #5	$23.92	6.262%	$25.4179	$25.42	$25.40	$25.40
Purchase #6	$26.46	9.145%	$28.8798	$28.88	$28.90	$28.90
Purchase #7	$236.29	4.737%	$247.4831	$247.48	$247.50	$247.50
7 purchase totals =	$1,001.72		$1,063.8246	$1,063.82	$1,063.80	$1,063.90