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	$92.41	9.767%	$101.4357	$101.44	$101.45	$101.40
Purchase #2	$124.73	5.538%	$131.6375	$131.64	$131.65	$131.60
Purchase #3	$82.26	8.404%	$89.1731	$89.17	$89.15	$89.20
Purchase #4	$35.89	5.518%	$37.8704	$37.87	$37.85	$37.90
Purchase #5	$99.57	3.270%	$102.8259	$102.83	$102.85	$102.80
Purchase #6	$162.29	3.796%	$168.4505	$168.45	$168.45	$168.50
Purchase #7	$44.75	13.187%	$50.6512	$50.65	$50.65	$50.70
7 purchase totals =	$641.90		$682.0443	$682.05	$682.05	$682.10