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	$89.46	6.798%	$95.5415	$95.54	$95.55	$95.50
Purchase #2	$28.79	13.320%	$32.6248	$32.62	$32.60	$32.60
Purchase #3	$97.52	7.597%	$104.9286	$104.93	$104.95	$104.90
Purchase #4	$190.38	3.458%	$196.9633	$196.96	$196.95	$197.00
Purchase #5	$40.31	13.617%	$45.799	$45.80	$45.80	$45.80
Purchase #6	$156.83	11.122%	$174.2726	$174.27	$174.25	$174.30
Purchase #7	$127.70	5.794%	$135.0989	$135.10	$135.10	$135.10
7 purchase totals =	$730.99		$785.2287	$785.22	$785.20	$785.20