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	$101.59	7.811%	$109.5252	$109.53	$109.55	$109.50
Purchase #2	$77.26	8.326%	$83.6927	$83.69	$83.70	$83.70
Purchase #3	$107.25	3.294%	$110.7828	$110.78	$110.80	$110.80
Purchase #4	$19.65	9.165%	$21.4509	$21.45	$21.45	$21.50
Purchase #5	$52.59	13.191%	$59.5271	$59.53	$59.55	$59.50
Purchase #6	$97.37	5.207%	$102.4401	$102.44	$102.45	$102.40
Purchase #7	$226.85	9.187%	$247.6907	$247.69	$247.70	$247.70
7 purchase totals =	$682.56		$735.1095	$735.11	$735.20	$735.10