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	$208.53	6.571%	$222.2325	$222.23	$222.25	$222.20
Purchase #2	$107.25	6.753%	$114.4926	$114.49	$114.50	$114.50
Purchase #3	$207.35	9.530%	$227.1105	$227.11	$227.10	$227.10
Purchase #4	$69.50	11.173%	$77.2652	$77.27	$77.25	$77.30
Purchase #5	$242.74	10.140%	$267.3538	$267.35	$267.35	$267.40
Purchase #6	$5.81	13.414%	$6.5894	$6.59	$6.60	$6.60
Purchase #7	$81.86	6.159%	$86.9018	$86.90	$86.90	$86.90
7 purchase totals =	$923.04		$1,001.9458	$1,001.94	$1,001.95	$1,002.00