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	$129.42	11.609%	$144.4444	$144.44	$144.45	$144.40
Purchase #2	$107.49	7.574%	$115.6313	$115.63	$115.65	$115.60
Purchase #3	$118.42	5.389%	$124.8017	$124.80	$124.80	$124.80
Purchase #4	$51.50	11.665%	$57.5075	$57.51	$57.50	$57.50
Purchase #5	$196.91	7.147%	$210.9832	$210.98	$211.00	$211.00
Purchase #6	$124.33	5.859%	$131.6145	$131.61	$131.60	$131.60
Purchase #7	$106.47	5.624%	$112.4579	$112.46	$112.45	$112.50
7 purchase totals =	$834.54		$897.4405	$897.43	$897.45	$897.40