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	$104.86	9.481%	$114.8018	$114.80	$114.80	$114.80
Purchase #2	$50.37	6.332%	$53.5594	$53.56	$53.55	$53.60
Purchase #3	$184.94	7.241%	$198.3315	$198.33	$198.35	$198.30
Purchase #4	$24.60	5.540%	$25.9628	$25.96	$25.95	$26.00
Purchase #5	$50.75	6.175%	$53.8838	$53.88	$53.90	$53.90
Purchase #6	$50.92	5.351%	$53.6447	$53.64	$53.65	$53.60
Purchase #7	$157.57	6.469%	$167.7632	$167.76	$167.75	$167.80
7 purchase totals =	$624.01		$667.9472	$667.93	$667.95	$668.00