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	$248.40	10.655%	$274.867	$274.87	$274.85	$274.90
Purchase #2	$211.27	12.599%	$237.8879	$237.89	$237.90	$237.90
Purchase #3	$82.27	5.252%	$86.5908	$86.59	$86.60	$86.60
Purchase #4	$157.28	13.523%	$178.549	$178.55	$178.55	$178.50
Purchase #5	$52.50	9.582%	$57.5306	$57.53	$57.55	$57.50
Purchase #6	$143.38	9.124%	$156.462	$156.46	$156.45	$156.50
Purchase #7	$81.87	11.431%	$91.2286	$91.23	$91.25	$91.20
7 purchase totals =	$976.97		$1,083.1159	$1,083.12	$1,083.15	$1,083.10