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	$211.90	5.725%	$224.0313	$224.03	$224.05	$224.00
Purchase #2	$218.25	4.181%	$227.375	$227.38	$227.40	$227.40
Purchase #3	$78.87	5.109%	$82.8995	$82.90	$82.90	$82.90
Purchase #4	$97.26	11.170%	$108.1239	$108.12	$108.10	$108.10
Purchase #5	$196.48	9.445%	$215.0375	$215.04	$215.05	$215.00
Purchase #6	$141.25	8.208%	$152.8438	$152.84	$152.85	$152.80
Purchase #7	$58.80	11.540%	$65.5855	$65.59	$65.60	$65.60
7 purchase totals =	$1,002.81		$1,075.8965	$1,075.90	$1,075.95	$1,075.80