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	$183.78	13.190%	$208.0206	$208.02	$208.00	$208.00
Purchase #2	$248.29	8.677%	$269.8341	$269.83	$269.85	$269.80
Purchase #3	$29.84	4.293%	$31.121	$31.12	$31.10	$31.10
Purchase #4	$57.65	8.798%	$62.722	$62.72	$62.70	$62.70
Purchase #5	$6.93	6.534%	$7.3828	$7.38	$7.40	$7.40
Purchase #6	$222.80	8.793%	$242.3908	$242.39	$242.40	$242.40
Purchase #7	$73.79	6.339%	$78.4675	$78.47	$78.45	$78.50
7 purchase totals =	$823.08		$899.9388	$899.93	$899.90	$899.90