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	$59.89	5.692%	$63.2989	$63.30	$63.30	$63.30
Purchase #2	$227.35	12.187%	$255.0571	$255.06	$255.05	$255.10
Purchase #3	$137.58	7.493%	$147.8889	$147.89	$147.90	$147.90
Purchase #4	$228.85	11.248%	$254.591	$254.59	$254.60	$254.60
Purchase #5	$147.46	8.241%	$159.6122	$159.61	$159.60	$159.60
Purchase #6	$61.36	5.621%	$64.809	$64.81	$64.80	$64.80
Purchase #7	$59.53	3.702%	$61.7338	$61.73	$61.75	$61.70
7 purchase totals =	$922.02		$1,006.9909	$1,006.99	$1,007.00	$1,007.00