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	$107.26	8.361%	$116.228	$116.23	$116.25	$116.20
Purchase #2	$73.64	6.430%	$78.3751	$78.38	$78.40	$78.40
Purchase #3	$45.99	8.521%	$49.9088	$49.91	$49.90	$49.90
Purchase #4	$82.30	6.715%	$87.8264	$87.83	$87.85	$87.80
Purchase #5	$227.44	7.420%	$244.316	$244.32	$244.30	$244.30
Purchase #6	$78.27	12.550%	$88.0929	$88.09	$88.10	$88.10
Purchase #7	$179.55	9.248%	$196.1548	$196.15	$196.15	$196.20
7 purchase totals =	$794.45		$860.9020	$860.91	$860.95	$860.90