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	$49.47	8.360%	$53.6057	$53.61	$53.60	$53.60
Purchase #2	$237.85	5.223%	$250.2729	$250.27	$250.25	$250.30
Purchase #3	$52.38	9.461%	$57.3357	$57.34	$57.35	$57.30
Purchase #4	$137.43	4.679%	$143.8603	$143.86	$143.85	$143.90
Purchase #5	$153.89	11.751%	$171.9736	$171.97	$171.95	$172.00
Purchase #6	$151.93	11.306%	$169.1072	$169.11	$169.10	$169.10
Purchase #7	$224.97	13.742%	$255.8854	$255.89	$255.90	$255.90
7 purchase totals =	$1,007.92		$1,102.0408	$1,102.05	$1,102.00	$1,102.10