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	$204.43	3.250%	$211.074	$211.07	$211.05	$211.10
Purchase #2	$238.80	9.658%	$261.8633	$261.86	$261.85	$261.90
Purchase #3	$194.88	11.670%	$217.6225	$217.62	$217.60	$217.60
Purchase #4	$161.89	3.379%	$167.3603	$167.36	$167.35	$167.40
Purchase #5	$51.64	3.127%	$53.2548	$53.25	$53.25	$53.30
Purchase #6	$64.38	5.256%	$67.7638	$67.76	$67.75	$67.80
Purchase #7	$33.36	9.849%	$36.6456	$36.65	$36.65	$36.60
7 purchase totals =	$949.38		$1,015.5843	$1,015.57	$1,015.50	$1,015.70