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	$211.93	13.503%	$240.5469	$240.55	$240.55	$240.50
Purchase #2	$219.31	4.614%	$229.429	$229.43	$229.45	$229.40
Purchase #3	$99.37	12.688%	$111.9781	$111.98	$112.00	$112.00
Purchase #4	$245.97	5.422%	$259.3065	$259.31	$259.30	$259.30
Purchase #5	$226.78	12.828%	$255.8713	$255.87	$255.85	$255.90
Purchase #6	$39.64	3.432%	$41.0004	$41.00	$41.00	$41.00
Purchase #7	$57.36	4.116%	$59.7209	$59.72	$59.70	$59.70
7 purchase totals =	$1,100.36		$1,197.8531	$1,197.86	$1,197.85	$1,197.80