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	$202.41	9.651%	$221.9446	$221.94	$221.95	$221.90
Purchase #2	$211.91	3.567%	$219.4688	$219.47	$219.45	$219.50
Purchase #3	$244.34	4.736%	$255.9119	$255.91	$255.90	$255.90
Purchase #4	$153.86	8.751%	$167.3243	$167.32	$167.30	$167.30
Purchase #5	$222.64	10.302%	$245.5764	$245.58	$245.60	$245.60
Purchase #6	$87.63	11.253%	$97.491	$97.49	$97.50	$97.50
Purchase #7	$158.85	8.649%	$172.5889	$172.59	$172.60	$172.60
7 purchase totals =	$1,281.64		$1,380.3059	$1,380.30	$1,380.30	$1,380.30