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	$126.64	10.681%	$140.1664	$140.17	$140.15	$140.20
Purchase #2	$145.38	8.733%	$158.076	$158.08	$158.10	$158.10
Purchase #3	$188.57	4.421%	$196.9067	$196.91	$196.90	$196.90
Purchase #4	$34.55	12.290%	$38.7962	$38.80	$38.80	$38.80
Purchase #5	$139.95	11.658%	$156.2654	$156.27	$156.25	$156.30
Purchase #6	$83.96	10.591%	$92.8522	$92.85	$92.85	$92.90
Purchase #7	$205.82	8.288%	$222.8784	$222.88	$222.90	$222.90
7 purchase totals =	$924.87		$1,005.9413	$1,005.96	$1,005.95	$1,006.10