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	$22.93	9.152%	$25.0286	$25.03	$25.05	$25.00
Purchase #2	$151.76	11.594%	$169.3551	$169.36	$169.35	$169.40
Purchase #3	$62.34	6.811%	$66.586	$66.59	$66.60	$66.60
Purchase #4	$205.55	9.620%	$225.3239	$225.32	$225.30	$225.30
Purchase #5	$176.89	5.632%	$186.8524	$186.85	$186.85	$186.90
Purchase #6	$237.68	4.619%	$248.6584	$248.66	$248.65	$248.70
Purchase #7	$183.59	7.251%	$196.9021	$196.90	$196.90	$196.90
7 purchase totals =	$1,040.74		$1,118.7065	$1,118.71	$1,118.70	$1,118.80