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	$142.39	7.680%	$153.3256	$153.33	$153.35	$153.30
Purchase #2	$99.37	12.785%	$112.0745	$112.07	$112.05	$112.10
Purchase #3	$177.47	4.692%	$185.7969	$185.80	$185.80	$185.80
Purchase #4	$157.94	6.692%	$168.5093	$168.51	$168.50	$168.50
Purchase #5	$6.39	9.450%	$6.9939	$6.99	$7.00	$7.00
Purchase #6	$102.26	8.597%	$111.0513	$111.05	$111.05	$111.10
Purchase #7	$25.63	5.760%	$27.1063	$27.11	$27.10	$27.10
7 purchase totals =	$711.45		$764.8578	$764.86	$764.85	$764.90